diff --git a/.gitignore b/.gitignore
index e660fd9..6df9c8e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 bin/
+.idea/
diff --git a/Makefile b/Makefile
index 68c5479..6320955 100644
--- a/Makefile
+++ b/Makefile
@@ -32,9 +32,9 @@ ci: dependencies test
 build-mocks:
 	@go get github.com/golang/mock/gomock
 	@go install github.com/golang/mock/mockgen
-	@~/go/bin/mockgen -source=domain/entity/book/interface.go -destination=domain/entity/book/mock/book.go -package=mock
-	@~/go/bin/mockgen -source=domain/entity/user/interface.go -destination=domain/entity/user/mock/user.go -package=mock
-	@~/go/bin/mockgen -source=domain/usecase/loan/interface.go -destination=domain/usecase/loan/mock/loan.go -package=mock
+	@~/go/bin/mockgen -source=usecase/book/interface.go -destination=usecase/book/mock/book.go -package=mock
+	@~/go/bin/mockgen -source=usecase/user/interface.go -destination=usecase/user/mock/user.go -package=mock
+	@~/go/bin/mockgen -source=usecase/loan/interface.go -destination=usecase/loan/mock/loan.go -package=mock
 
 test:
 	go test -tags testing ./...
diff --git a/api/handler/book.go b/api/handler/book.go
index a3947ad..f6dc6f8 100644
--- a/api/handler/book.go
+++ b/api/handler/book.go
@@ -4,33 +4,30 @@ import (
 	"encoding/json"
 	"log"
 	"net/http"
-	"time"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/book"
 
 	"github.com/eminetto/clean-architecture-go-v2/api/presenter"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-
 	"github.com/codegangsta/negroni"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 	"github.com/gorilla/mux"
 )
 
-func listBooks(manager book.Manager) http.Handler {
+func listBooks(service book.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error reading books"
-		var data []*book.Book
+		var data []*entity.Book
 		var err error
 		title := r.URL.Query().Get("title")
 		switch {
 		case title == "":
-			data, err = manager.List()
+			data, err = service.ListBooks()
 		default:
-			data, err = manager.Search(title)
+			data, err = service.SearchBooks(title)
 		}
 		w.Header().Set("Content-Type", "application/json")
-		if err != nil && err != domain.ErrNotFound {
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -58,7 +55,7 @@ func listBooks(manager book.Manager) http.Handler {
 	})
 }
 
-func createBook(manager book.Manager) http.Handler {
+func createBook(service book.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error adding book"
 		var input struct {
@@ -74,27 +71,18 @@ func createBook(manager book.Manager) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		b := &book.Book{
-			ID:        entity.NewID(),
-			Title:     input.Title,
-			Author:    input.Author,
-			Pages:     input.Pages,
-			Quantity:  input.Quantity,
-			CreatedAt: time.Now(),
-		}
-		b.ID, err = manager.Create(b)
+		id, err := service.CreateBook(input.Title, input.Author, input.Pages, input.Quantity)
 		if err != nil {
-			log.Println(err.Error())
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
 		}
 		toJ := &presenter.Book{
-			ID:       b.ID,
-			Title:    b.Title,
-			Author:   b.Author,
-			Pages:    b.Pages,
-			Quantity: b.Quantity,
+			ID:       id,
+			Title:    input.Title,
+			Author:   input.Author,
+			Pages:    input.Pages,
+			Quantity: input.Quantity,
 		}
 
 		w.WriteHeader(http.StatusCreated)
@@ -107,7 +95,7 @@ func createBook(manager book.Manager) http.Handler {
 	})
 }
 
-func getBook(manager book.Manager) http.Handler {
+func getBook(service book.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error reading book"
 		vars := mux.Vars(r)
@@ -117,8 +105,8 @@ func getBook(manager book.Manager) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		data, err := manager.Get(id)
-		if err != nil && err != domain.ErrNotFound {
+		data, err := service.GetBook(id)
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -143,7 +131,7 @@ func getBook(manager book.Manager) http.Handler {
 	})
 }
 
-func deleteBook(manager book.Manager) http.Handler {
+func deleteBook(service book.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error removing bookmark"
 		vars := mux.Vars(r)
@@ -153,7 +141,7 @@ func deleteBook(manager book.Manager) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		err = manager.Delete(id)
+		err = service.DeleteBook(id)
 		if err != nil {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
@@ -163,20 +151,20 @@ func deleteBook(manager book.Manager) http.Handler {
 }
 
 //MakeBookHandlers make url handlers
-func MakeBookHandlers(r *mux.Router, n negroni.Negroni, manager book.Manager) {
+func MakeBookHandlers(r *mux.Router, n negroni.Negroni, service book.UseCase) {
 	r.Handle("/v1/book", n.With(
-		negroni.Wrap(listBooks(manager)),
+		negroni.Wrap(listBooks(service)),
 	)).Methods("GET", "OPTIONS").Name("listBooks")
 
 	r.Handle("/v1/book", n.With(
-		negroni.Wrap(createBook(manager)),
+		negroni.Wrap(createBook(service)),
 	)).Methods("POST", "OPTIONS").Name("createBook")
 
 	r.Handle("/v1/book/{id}", n.With(
-		negroni.Wrap(getBook(manager)),
+		negroni.Wrap(getBook(service)),
 	)).Methods("GET", "OPTIONS").Name("getBook")
 
 	r.Handle("/v1/book/{id}", n.With(
-		negroni.Wrap(deleteBook(manager)),
+		negroni.Wrap(deleteBook(service)),
 	)).Methods("DELETE", "OPTIONS").Name("deleteBook")
 }
diff --git a/api/handler/book_test.go b/api/handler/book_test.go
index 9794b4d..cf2c6b5 100644
--- a/api/handler/book_test.go
+++ b/api/handler/book_test.go
@@ -8,13 +8,10 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 
 	"github.com/codegangsta/negroni"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book/mock"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/book/mock"
 	"github.com/golang/mock/gomock"
 	"github.com/gorilla/mux"
 	"github.com/stretchr/testify/assert"
@@ -23,18 +20,20 @@ import (
 func Test_listBooks(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	manager := mock.NewMockManager(controller)
+	service := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
-	MakeBookHandlers(r, *n, manager)
+	MakeBookHandlers(r, *n, service)
 	path, err := r.GetRoute("listBooks").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/book", path)
-	b := book.NewFixtureBook()
-	manager.EXPECT().
-		List().
-		Return([]*book.Book{b}, nil)
-	ts := httptest.NewServer(listBooks(manager))
+	b := &entity.Book{
+		ID: entity.NewID(),
+	}
+	service.EXPECT().
+		ListBooks().
+		Return([]*entity.Book{b}, nil)
+	ts := httptest.NewServer(listBooks(service))
 	defer ts.Close()
 	res, err := http.Get(ts.URL)
 	assert.Nil(t, err)
@@ -44,12 +43,12 @@ func Test_listBooks(t *testing.T) {
 func Test_listBooks_NotFound(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	manager := mock.NewMockManager(controller)
-	ts := httptest.NewServer(listBooks(manager))
+	service := mock.NewMockUseCase(controller)
+	ts := httptest.NewServer(listBooks(service))
 	defer ts.Close()
-	manager.EXPECT().
-		Search("book of books").
-		Return(nil, domain.ErrNotFound)
+	service.EXPECT().
+		SearchBooks("book of books").
+		Return(nil, entity.ErrNotFound)
 	res, err := http.Get(ts.URL + "?title=book+of+books")
 	assert.Nil(t, err)
 	assert.Equal(t, http.StatusNotFound, res.StatusCode)
@@ -58,12 +57,14 @@ func Test_listBooks_NotFound(t *testing.T) {
 func Test_listBooks_Search(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	manager := mock.NewMockManager(controller)
-	b := book.NewFixtureBook()
-	manager.EXPECT().
-		Search("ozzy").
-		Return([]*book.Book{b}, nil)
-	ts := httptest.NewServer(listBooks(manager))
+	service := mock.NewMockUseCase(controller)
+	b := &entity.Book{
+		ID: entity.NewID(),
+	}
+	service.EXPECT().
+		SearchBooks("ozzy").
+		Return([]*entity.Book{b}, nil)
+	ts := httptest.NewServer(listBooks(service))
 	defer ts.Close()
 	res, err := http.Get(ts.URL + "?title=ozzy")
 	assert.Nil(t, err)
@@ -73,18 +74,18 @@ func Test_listBooks_Search(t *testing.T) {
 func Test_createBook(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	manager := mock.NewMockManager(controller)
+	service := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
-	MakeBookHandlers(r, *n, manager)
+	MakeBookHandlers(r, *n, service)
 	path, err := r.GetRoute("createBook").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/book", path)
 
-	manager.EXPECT().
-		Create(gomock.Any()).
+	service.EXPECT().
+		CreateBook(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).
 		Return(entity.NewID(), nil)
-	h := createBook(manager)
+	h := createBook(service)
 
 	ts := httptest.NewServer(h)
 	defer ts.Close()
@@ -97,7 +98,7 @@ func Test_createBook(t *testing.T) {
 	resp, _ := http.Post(ts.URL+"/v1/book", "application/json", strings.NewReader(payload))
 	assert.Equal(t, http.StatusCreated, resp.StatusCode)
 
-	var b *book.Book
+	var b *entity.Book
 	json.NewDecoder(resp.Body).Decode(&b)
 	assert.Equal(t, "Ozzy Osbourne", b.Author)
 }
@@ -105,25 +106,27 @@ func Test_createBook(t *testing.T) {
 func Test_getBook(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	manager := mock.NewMockManager(controller)
+	service := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
-	MakeBookHandlers(r, *n, manager)
+	MakeBookHandlers(r, *n, service)
 	path, err := r.GetRoute("getBook").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/book/{id}", path)
-	b := book.NewFixtureBook()
-	manager.EXPECT().
-		Get(b.ID).
+	b := &entity.Book{
+		ID: entity.NewID(),
+	}
+	service.EXPECT().
+		GetBook(b.ID).
 		Return(b, nil)
-	handler := getBook(manager)
+	handler := getBook(service)
 	r.Handle("/v1/book/{id}", handler)
 	ts := httptest.NewServer(r)
 	defer ts.Close()
 	res, err := http.Get(ts.URL + "/v1/book/" + b.ID.String())
 	assert.Nil(t, err)
 	assert.Equal(t, http.StatusOK, res.StatusCode)
-	var d *book.Book
+	var d *entity.Book
 	json.NewDecoder(res.Body).Decode(&d)
 	assert.NotNil(t, d)
 	assert.Equal(t, b.ID, d.ID)
@@ -132,16 +135,18 @@ func Test_getBook(t *testing.T) {
 func Test_deleteBook(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	manager := mock.NewMockManager(controller)
+	service := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
-	MakeBookHandlers(r, *n, manager)
+	MakeBookHandlers(r, *n, service)
 	path, err := r.GetRoute("deleteBook").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/book/{id}", path)
-	b := book.NewFixtureBook()
-	manager.EXPECT().Delete(b.ID).Return(nil)
-	handler := deleteBook(manager)
+	b := &entity.Book{
+		ID: entity.NewID(),
+	}
+	service.EXPECT().DeleteBook(b.ID).Return(nil)
+	handler := deleteBook(service)
 	req, _ := http.NewRequest("DELETE", "/v1/bookmark/"+b.ID.String(), nil)
 	r.Handle("/v1/bookmark/{id}", handler).Methods("DELETE", "OPTIONS")
 	rr := httptest.NewRecorder()
diff --git a/api/handler/loan.go b/api/handler/loan.go
index 639f7d0..16ea7e0 100644
--- a/api/handler/loan.go
+++ b/api/handler/loan.go
@@ -4,20 +4,17 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/book"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/user"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/usecase/loan"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/loan"
 
 	"github.com/codegangsta/negroni"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 	"github.com/gorilla/mux"
 )
 
-func borrowBook(bManager book.Manager, uManager user.Manager, loanUseCase loan.UseCase) http.Handler {
+func borrowBook(bookService book.UseCase, userService user.UseCase, loanService loan.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error borrowing book"
 		vars := mux.Vars(r)
@@ -27,8 +24,8 @@ func borrowBook(bManager book.Manager, uManager user.Manager, loanUseCase loan.U
 			w.Write([]byte(errorMessage))
 			return
 		}
-		b, err := bManager.Get(bID)
-		if err != nil && err != domain.ErrNotFound {
+		b, err := bookService.GetBook(bID)
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -44,8 +41,8 @@ func borrowBook(bManager book.Manager, uManager user.Manager, loanUseCase loan.U
 			w.Write([]byte(errorMessage))
 			return
 		}
-		u, err := uManager.Get(uID)
-		if err != nil && err != domain.ErrNotFound {
+		u, err := userService.GetUser(uID)
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -55,7 +52,7 @@ func borrowBook(bManager book.Manager, uManager user.Manager, loanUseCase loan.U
 			w.Write([]byte(errorMessage))
 			return
 		}
-		err = loanUseCase.Borrow(u, b)
+		err = loanService.Borrow(u, b)
 		if err != nil {
 			fmt.Println(err)
 			w.WriteHeader(http.StatusInternalServerError)
@@ -66,7 +63,7 @@ func borrowBook(bManager book.Manager, uManager user.Manager, loanUseCase loan.U
 	})
 }
 
-func returnBook(bManager book.Manager, loanUseCase loan.UseCase) http.Handler {
+func returnBook(bookService book.UseCase, loanService loan.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error returning book"
 		vars := mux.Vars(r)
@@ -76,8 +73,8 @@ func returnBook(bManager book.Manager, loanUseCase loan.UseCase) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		b, err := bManager.Get(bID)
-		if err != nil && err != domain.ErrNotFound {
+		b, err := bookService.GetBook(bID)
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -87,8 +84,8 @@ func returnBook(bManager book.Manager, loanUseCase loan.UseCase) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		err = loanUseCase.Return(b)
-		if err != nil && err != domain.ErrNotFound {
+		err = loanService.Return(b)
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -98,12 +95,12 @@ func returnBook(bManager book.Manager, loanUseCase loan.UseCase) http.Handler {
 }
 
 //MakeLoanHandlers make url handlers
-func MakeLoanHandlers(r *mux.Router, n negroni.Negroni, bManager book.Manager, uManager user.Manager, loanUseCase loan.UseCase) {
+func MakeLoanHandlers(r *mux.Router, n negroni.Negroni, bookService book.UseCase, userService user.UseCase, loanService loan.UseCase) {
 	r.Handle("/v1/loan/borrow/{book_id}/{user_id}", n.With(
-		negroni.Wrap(borrowBook(bManager, uManager, loanUseCase)),
+		negroni.Wrap(borrowBook(bookService, userService, loanService)),
 	)).Methods("GET", "OPTIONS").Name("borrowBook")
 
 	r.Handle("/v1/loan/return/{book_id}", n.With(
-		negroni.Wrap(returnBook(bManager, loanUseCase)),
+		negroni.Wrap(returnBook(bookService, loanService)),
 	)).Methods("GET", "OPTIONS").Name("returnBook")
 }
diff --git a/api/handler/loan_test.go b/api/handler/loan_test.go
index 5f28b61..7131c9c 100644
--- a/api/handler/loan_test.go
+++ b/api/handler/loan_test.go
@@ -6,17 +6,12 @@ import (
 	"net/http/httptest"
 	"testing"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 
 	"github.com/codegangsta/negroni"
-	bmock "github.com/eminetto/clean-architecture-go-v2/domain/entity/book/mock"
-	umock "github.com/eminetto/clean-architecture-go-v2/domain/entity/user/mock"
-	lmock "github.com/eminetto/clean-architecture-go-v2/domain/usecase/loan/mock"
+	bmock "github.com/eminetto/clean-architecture-go-v2/usecase/book/mock"
+	lmock "github.com/eminetto/clean-architecture-go-v2/usecase/loan/mock"
+	umock "github.com/eminetto/clean-architecture-go-v2/usecase/user/mock"
 	"github.com/golang/mock/gomock"
 	"github.com/gorilla/mux"
 	"github.com/stretchr/testify/assert"
@@ -25,8 +20,8 @@ import (
 func Test_borrowBook(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	uMock := umock.NewMockManager(controller)
-	bMock := bmock.NewMockManager(controller)
+	uMock := umock.NewMockUseCase(controller)
+	bMock := bmock.NewMockUseCase(controller)
 	lMock := lmock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
@@ -39,7 +34,7 @@ func Test_borrowBook(t *testing.T) {
 	t.Run("book not found", func(t *testing.T) {
 		bID := entity.NewID()
 		uID := entity.NewID()
-		bMock.EXPECT().Get(bID).Return(nil, domain.ErrNotFound)
+		bMock.EXPECT().GetBook(bID).Return(nil, entity.ErrNotFound)
 		ts := httptest.NewServer(r)
 		defer ts.Close()
 		res, err := http.Get(fmt.Sprintf("%s/v1/loan/borrow/%s/%s", ts.URL, bID.String(), uID.String()))
@@ -47,10 +42,12 @@ func Test_borrowBook(t *testing.T) {
 		assert.Equal(t, http.StatusNotFound, res.StatusCode)
 	})
 	t.Run("user not found", func(t *testing.T) {
-		b := book.NewFixtureBook()
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
 		uID := entity.NewID()
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		uMock.EXPECT().Get(uID).Return(nil, domain.ErrNotFound)
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		uMock.EXPECT().GetUser(uID).Return(nil, entity.ErrNotFound)
 		ts := httptest.NewServer(r)
 		defer ts.Close()
 		res, err := http.Get(fmt.Sprintf("%s/v1/loan/borrow/%s/%s", ts.URL, b.ID.String(), uID.String()))
@@ -58,10 +55,14 @@ func Test_borrowBook(t *testing.T) {
 		assert.Equal(t, http.StatusNotFound, res.StatusCode)
 	})
 	t.Run("success", func(t *testing.T) {
-		b := book.NewFixtureBook()
-		u := user.NewFixtureUser()
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		uMock.EXPECT().Get(u.ID).Return(u, nil)
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		uMock.EXPECT().GetUser(u.ID).Return(u, nil)
 		lMock.EXPECT().Borrow(u, b).Return(nil)
 		ts := httptest.NewServer(r)
 		defer ts.Close()
@@ -74,8 +75,8 @@ func Test_borrowBook(t *testing.T) {
 func Test_returnBook(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	uMock := umock.NewMockManager(controller)
-	bMock := bmock.NewMockManager(controller)
+	uMock := umock.NewMockUseCase(controller)
+	bMock := bmock.NewMockUseCase(controller)
 	lMock := lmock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
@@ -87,7 +88,7 @@ func Test_returnBook(t *testing.T) {
 	r.Handle("/v1/loan/return/{book_id}", handler)
 	t.Run("book not found", func(t *testing.T) {
 		bID := entity.NewID()
-		bMock.EXPECT().Get(bID).Return(nil, domain.ErrNotFound)
+		bMock.EXPECT().GetBook(bID).Return(nil, entity.ErrNotFound)
 		ts := httptest.NewServer(r)
 		defer ts.Close()
 		res, err := http.Get(fmt.Sprintf("%s/v1/loan/return/%s", ts.URL, bID.String()))
@@ -95,8 +96,10 @@ func Test_returnBook(t *testing.T) {
 		assert.Equal(t, http.StatusNotFound, res.StatusCode)
 	})
 	t.Run("success", func(t *testing.T) {
-		b := book.NewFixtureBook()
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
 		lMock.EXPECT().Return(b).Return(nil)
 		ts := httptest.NewServer(r)
 		defer ts.Close()
diff --git a/api/handler/user.go b/api/handler/user.go
index 6c7f2a0..4b1b45f 100644
--- a/api/handler/user.go
+++ b/api/handler/user.go
@@ -4,34 +4,31 @@ import (
 	"encoding/json"
 	"log"
 	"net/http"
-	"time"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/user"
 
 	"github.com/eminetto/clean-architecture-go-v2/api/presenter"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 
 	"github.com/codegangsta/negroni"
 	"github.com/gorilla/mux"
 )
 
-func listUsers(manager user.Manager) http.Handler {
+func listUsers(service user.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error reading users"
-		var data []*user.User
+		var data []*entity.User
 		var err error
 		name := r.URL.Query().Get("name")
 		switch {
 		case name == "":
-			data, err = manager.List()
+			data, err = service.ListUsers()
 		default:
-			data, err = manager.Search(name)
+			data, err = service.SearchUsers(name)
 		}
 		w.Header().Set("Content-Type", "application/json")
-		if err != nil && err != domain.ErrNotFound {
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -58,7 +55,7 @@ func listUsers(manager user.Manager) http.Handler {
 	})
 }
 
-func createUser(manager user.Manager) http.Handler {
+func createUser(service user.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error adding user"
 		var input struct {
@@ -74,16 +71,7 @@ func createUser(manager user.Manager) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		//TODO: validate data ;)
-		u := &user.User{
-			ID:        entity.NewID(),
-			Email:     input.Email,
-			Password:  input.Password,
-			FirstName: input.FirstName,
-			LastName:  input.LastName,
-			CreatedAt: time.Now(),
-		}
-		u.ID, err = manager.Create(u)
+		id, err := service.CreateUser(input.Email, input.Password, input.FirstName, input.LastName)
 		if err != nil {
 			log.Println(err.Error())
 			w.WriteHeader(http.StatusInternalServerError)
@@ -91,15 +79,14 @@ func createUser(manager user.Manager) http.Handler {
 			return
 		}
 		toJ := &presenter.User{
-			ID:        u.ID,
-			Email:     u.Email,
-			FirstName: u.FirstName,
-			LastName:  u.LastName,
+			ID:        id,
+			Email:     input.Email,
+			FirstName: input.FirstName,
+			LastName:  input.LastName,
 		}
 
 		w.WriteHeader(http.StatusCreated)
 		if err := json.NewEncoder(w).Encode(toJ); err != nil {
-			log.Println(err.Error())
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -107,7 +94,7 @@ func createUser(manager user.Manager) http.Handler {
 	})
 }
 
-func getUser(manager user.Manager) http.Handler {
+func getUser(service user.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error reading user"
 		vars := mux.Vars(r)
@@ -117,9 +104,9 @@ func getUser(manager user.Manager) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		data, err := manager.Get(id)
+		data, err := service.GetUser(id)
 		w.Header().Set("Content-Type", "application/json")
-		if err != nil && err != domain.ErrNotFound {
+		if err != nil && err != entity.ErrNotFound {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
 			return
@@ -143,7 +130,7 @@ func getUser(manager user.Manager) http.Handler {
 	})
 }
 
-func deleteUser(manager user.Manager) http.Handler {
+func deleteUser(service user.UseCase) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		errorMessage := "Error removing user"
 		vars := mux.Vars(r)
@@ -153,7 +140,7 @@ func deleteUser(manager user.Manager) http.Handler {
 			w.Write([]byte(errorMessage))
 			return
 		}
-		err = manager.Delete(id)
+		err = service.DeleteUser(id)
 		if err != nil {
 			w.WriteHeader(http.StatusInternalServerError)
 			w.Write([]byte(errorMessage))
@@ -163,20 +150,20 @@ func deleteUser(manager user.Manager) http.Handler {
 }
 
 //MakeUserHandlers make url handlers
-func MakeUserHandlers(r *mux.Router, n negroni.Negroni, manager user.Manager) {
+func MakeUserHandlers(r *mux.Router, n negroni.Negroni, service user.UseCase) {
 	r.Handle("/v1/user", n.With(
-		negroni.Wrap(listUsers(manager)),
+		negroni.Wrap(listUsers(service)),
 	)).Methods("GET", "OPTIONS").Name("listUsers")
 
 	r.Handle("/v1/user", n.With(
-		negroni.Wrap(createUser(manager)),
+		negroni.Wrap(createUser(service)),
 	)).Methods("POST", "OPTIONS").Name("createUser")
 
 	r.Handle("/v1/user/{id}", n.With(
-		negroni.Wrap(getUser(manager)),
+		negroni.Wrap(getUser(service)),
 	)).Methods("GET", "OPTIONS").Name("getUser")
 
 	r.Handle("/v1/user/{id}", n.With(
-		negroni.Wrap(deleteUser(manager)),
+		negroni.Wrap(deleteUser(service)),
 	)).Methods("DELETE", "OPTIONS").Name("deleteUser")
 }
diff --git a/api/handler/user_test.go b/api/handler/user_test.go
index 64dcd54..05b06de 100644
--- a/api/handler/user_test.go
+++ b/api/handler/user_test.go
@@ -10,10 +10,8 @@ import (
 
 	"github.com/codegangsta/negroni"
 	"github.com/eminetto/clean-architecture-go-v2/api/presenter"
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user/mock"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/user/mock"
 	"github.com/golang/mock/gomock"
 	"github.com/gorilla/mux"
 	"github.com/stretchr/testify/assert"
@@ -22,17 +20,19 @@ import (
 func Test_listUsers(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	m := mock.NewMockManager(controller)
+	m := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
 	MakeUserHandlers(r, *n, m)
 	path, err := r.GetRoute("listUsers").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/user", path)
-	u := user.NewFixtureUser()
+	u := &entity.User{
+		ID: entity.NewID(),
+	}
 	m.EXPECT().
-		List().
-		Return([]*user.User{u}, nil)
+		ListUsers().
+		Return([]*entity.User{u}, nil)
 	ts := httptest.NewServer(listUsers(m))
 	defer ts.Close()
 	res, err := http.Get(ts.URL)
@@ -43,12 +43,12 @@ func Test_listUsers(t *testing.T) {
 func Test_listUsers_NotFound(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	m := mock.NewMockManager(controller)
+	m := mock.NewMockUseCase(controller)
 	ts := httptest.NewServer(listUsers(m))
 	defer ts.Close()
 	m.EXPECT().
-		Search("dio").
-		Return(nil, domain.ErrNotFound)
+		SearchUsers("dio").
+		Return(nil, entity.ErrNotFound)
 	res, err := http.Get(ts.URL + "?name=dio")
 	assert.Nil(t, err)
 	assert.Equal(t, http.StatusNotFound, res.StatusCode)
@@ -57,11 +57,13 @@ func Test_listUsers_NotFound(t *testing.T) {
 func Test_listUsers_Search(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	m := mock.NewMockManager(controller)
-	u := user.NewFixtureUser()
+	m := mock.NewMockUseCase(controller)
+	u := &entity.User{
+		ID: entity.NewID(),
+	}
 	m.EXPECT().
-		Search("ozzy").
-		Return([]*user.User{u}, nil)
+		SearchUsers("ozzy").
+		Return([]*entity.User{u}, nil)
 	ts := httptest.NewServer(listUsers(m))
 	defer ts.Close()
 	res, err := http.Get(ts.URL + "?name=ozzy")
@@ -72,7 +74,7 @@ func Test_listUsers_Search(t *testing.T) {
 func Test_createUser(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	m := mock.NewMockManager(controller)
+	m := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
 	MakeUserHandlers(r, *n, m)
@@ -81,7 +83,7 @@ func Test_createUser(t *testing.T) {
 	assert.Equal(t, "/v1/user", path)
 
 	m.EXPECT().
-		Create(gomock.Any()).
+		CreateUser(gomock.Any(), gomock.Any(), gomock.Any(), gomock.Any()).
 		Return(entity.NewID(), nil)
 	h := createUser(m)
 
@@ -105,16 +107,18 @@ func Test_createUser(t *testing.T) {
 func Test_getUser(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	m := mock.NewMockManager(controller)
+	m := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
 	MakeUserHandlers(r, *n, m)
 	path, err := r.GetRoute("getUser").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/user/{id}", path)
-	u := user.NewFixtureUser()
+	u := &entity.User{
+		ID: entity.NewID(),
+	}
 	m.EXPECT().
-		Get(u.ID).
+		GetUser(u.ID).
 		Return(u, nil)
 	handler := getUser(m)
 	r.Handle("/v1/user/{id}", handler)
@@ -132,15 +136,17 @@ func Test_getUser(t *testing.T) {
 func Test_deleteUser(t *testing.T) {
 	controller := gomock.NewController(t)
 	defer controller.Finish()
-	m := mock.NewMockManager(controller)
+	m := mock.NewMockUseCase(controller)
 	r := mux.NewRouter()
 	n := negroni.New()
 	MakeUserHandlers(r, *n, m)
 	path, err := r.GetRoute("deleteUser").GetPathTemplate()
 	assert.Nil(t, err)
 	assert.Equal(t, "/v1/user/{id}", path)
-	u := user.NewFixtureUser()
-	m.EXPECT().Delete(u.ID).Return(nil)
+	u := &entity.User{
+		ID: entity.NewID(),
+	}
+	m.EXPECT().DeleteUser(u.ID).Return(nil)
 	handler := deleteUser(m)
 	req, _ := http.NewRequest("DELETE", "/v1/user/"+u.ID.String(), nil)
 	r.Handle("/v1/user/{id}", handler).Methods("DELETE", "OPTIONS")
diff --git a/api/main.go b/api/main.go
index d040ef1..20ab983 100644
--- a/api/main.go
+++ b/api/main.go
@@ -9,13 +9,12 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/eminetto/clean-architecture-go-v2/pkg/password"
+	"github.com/eminetto/clean-architecture-go-v2/driver/repository"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/book"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/user"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/usecase/loan"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/loan"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
 	"github.com/prometheus/client_golang/prometheus/promhttp"
 
 	"github.com/codegangsta/negroni"
@@ -37,13 +36,13 @@ func main() {
 	}
 	defer db.Close()
 
-	bookRepo := book.NewMySQLRepository(db)
-	bookManager := book.NewManager(bookRepo)
+	bookRepo := repository.NewBookMySQL(db)
+	bookService := book.NewService(bookRepo)
 
-	userRepo := user.NewMySQLRepoRepository(db)
-	userManager := user.NewManager(userRepo, password.NewService())
+	userRepo := repository.NewUserMySQL(db)
+	userService := user.NewService(userRepo)
 
-	loanUseCase := loan.NewUseCase(userManager, bookManager)
+	loanUseCase := loan.NewService(userService, bookService)
 
 	metricService, err := metric.NewPrometheusService()
 	if err != nil {
@@ -57,13 +56,13 @@ func main() {
 		negroni.NewLogger(),
 	)
 	//book
-	handler.MakeBookHandlers(r, *n, bookManager)
+	handler.MakeBookHandlers(r, *n, bookService)
 
 	//user
-	handler.MakeUserHandlers(r, *n, userManager)
+	handler.MakeUserHandlers(r, *n, userService)
 
 	//loan
-	handler.MakeLoanHandlers(r, *n, bookManager, userManager, loanUseCase)
+	handler.MakeLoanHandlers(r, *n, bookService, userService, loanUseCase)
 
 	http.Handle("/", r)
 	http.Handle("/metrics", promhttp.Handler())
diff --git a/api/presenter/book.go b/api/presenter/book.go
index 257c7e5..ba52eb3 100644
--- a/api/presenter/book.go
+++ b/api/presenter/book.go
@@ -1,7 +1,7 @@
 package presenter
 
 import (
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 )
 
 //Book data
diff --git a/api/presenter/user.go b/api/presenter/user.go
index 05dfb3e..bf4b97e 100644
--- a/api/presenter/user.go
+++ b/api/presenter/user.go
@@ -1,7 +1,7 @@
 package presenter
 
 import (
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 )
 
 //User data
diff --git a/cmd/main.go b/cmd/main.go
index ff2696d..f1041d7 100644
--- a/cmd/main.go
+++ b/cmd/main.go
@@ -7,11 +7,12 @@ import (
 	"log"
 	"os"
 
+	"github.com/eminetto/clean-architecture-go-v2/driver/repository"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/book"
+
 	"github.com/eminetto/clean-architecture-go-v2/config"
 	_ "github.com/go-sql-driver/mysql"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-
 	"github.com/eminetto/clean-architecture-go-v2/pkg/metric"
 )
 
@@ -40,9 +41,9 @@ func main() {
 		log.Fatal(err.Error())
 	}
 	defer db.Close()
-	repo := book.NewMySQLRepository(db)
-	manager := book.NewManager(repo)
-	all, err := manager.Search(query)
+	repo := repository.NewBookMySQL(db)
+	service := book.NewService(repo)
+	all, err := service.SearchBooks(query)
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/docker-compose.yml b/docker-compose.yml
index 6894b3b..82d0aab 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -4,7 +4,7 @@ services:
     image: mysql:5.7
     command: --default-authentication-plugin=mysql_native_password --init-file /data/application/init.sql
     volumes:
-      - ./infra/init.sql:/data/application/init.sql
+      - ./ops/init.sql:/data/application/init.sql
     environment:
       MYSQL_ROOT_PASSWORD: clean_architecture_go_v2
       MYSQL_DATABASE: clean_architecture_go_v2
@@ -30,7 +30,7 @@ services:
     command:
       - --config.file=/etc/prometheus/prometheus.yml
     volumes:
-      - ./infra/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml:ro
+      - ./ops/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml:ro
     container_name: clean-architecture-go-v2-prometheus
     network_mode: "bridge"
   prometheus-pushgateway:
diff --git a/domain/entity/book/entity.go b/domain/entity/book/entity.go
deleted file mode 100644
index cd6a575..0000000
--- a/domain/entity/book/entity.go
+++ /dev/null
@@ -1,18 +0,0 @@
-package book
-
-import (
-	"time"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-//Book data
-type Book struct {
-	ID        entity.ID
-	Title     string
-	Author    string
-	Pages     int
-	Quantity  int
-	CreatedAt time.Time
-	UpdatedAt time.Time
-}
diff --git a/domain/entity/book/fixture.go b/domain/entity/book/fixture.go
deleted file mode 100644
index 97a3bca..0000000
--- a/domain/entity/book/fixture.go
+++ /dev/null
@@ -1,18 +0,0 @@
-package book
-
-import (
-	"time"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-func NewFixtureBook() *Book {
-	return &Book{
-		ID:        entity.NewID(),
-		Title:     "I Am Ozzy",
-		Author:    "Ozzy Osbourne",
-		Pages:     294,
-		Quantity:  1,
-		CreatedAt: time.Now(),
-	}
-}
diff --git a/domain/entity/book/interface.go b/domain/entity/book/interface.go
deleted file mode 100644
index 233e6cb..0000000
--- a/domain/entity/book/interface.go
+++ /dev/null
@@ -1,28 +0,0 @@
-package book
-
-import "github.com/eminetto/clean-architecture-go-v2/domain/entity"
-
-//Reader interface
-type Reader interface {
-	Get(id entity.ID) (*Book, error)
-	Search(query string) ([]*Book, error)
-	List() ([]*Book, error)
-}
-
-//Writer book writer
-type Writer interface {
-	Create(e *Book) (entity.ID, error)
-	Update(e *Book) error
-	Delete(id entity.ID) error
-}
-
-//repository interface
-type repository interface {
-	Reader
-	Writer
-}
-
-//Manager interface
-type Manager interface {
-	repository
-}
diff --git a/domain/entity/book/manager.go b/domain/entity/book/manager.go
deleted file mode 100644
index 893dc2b..0000000
--- a/domain/entity/book/manager.go
+++ /dev/null
@@ -1,55 +0,0 @@
-package book
-
-import (
-	"strings"
-	"time"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-type manager struct {
-	repo repository
-}
-
-//NewManager create new manager
-func NewManager(r repository) *manager {
-	return &manager{
-		repo: r,
-	}
-}
-
-//Create a book
-func (s *manager) Create(e *Book) (entity.ID, error) {
-	e.ID = entity.NewID()
-	e.CreatedAt = time.Now()
-	return s.repo.Create(e)
-}
-
-//Get a book
-func (s *manager) Get(id entity.ID) (*Book, error) {
-	return s.repo.Get(id)
-}
-
-//Search books
-func (s *manager) Search(query string) ([]*Book, error) {
-	return s.repo.Search(strings.ToLower(query))
-}
-
-//List books
-func (s *manager) List() ([]*Book, error) {
-	return s.repo.List()
-}
-
-//Delete a book
-func (s *manager) Delete(id entity.ID) error {
-	_, err := s.Get(id)
-	if err != nil {
-		return err
-	}
-	return s.repo.Delete(id)
-}
-
-//Update a book
-func (s *manager) Update(e *Book) error {
-	return s.repo.Update(e)
-}
diff --git a/domain/entity/book/manager_test.go b/domain/entity/book/manager_test.go
deleted file mode 100644
index 2249154..0000000
--- a/domain/entity/book/manager_test.go
+++ /dev/null
@@ -1,82 +0,0 @@
-package book
-
-import (
-	"testing"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func Test_Create(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo)
-	u := NewFixtureBook()
-	id, err := m.Create(u)
-	assert.Nil(t, err)
-	assert.Equal(t, u.ID, id)
-	assert.False(t, u.CreatedAt.IsZero())
-}
-
-func Test_SearchAndFind(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo)
-	u1 := NewFixtureBook()
-	u2 := NewFixtureBook()
-	u2.Title = "Lemmy: Biography"
-
-	uID, _ := m.Create(u1)
-	_, _ = m.Create(u2)
-
-	t.Run("search", func(t *testing.T) {
-		c, err := m.Search("ozzy")
-		assert.Nil(t, err)
-		assert.Equal(t, 1, len(c))
-		assert.Equal(t, "I Am Ozzy", c[0].Title)
-
-		c, err = m.Search("dio")
-		assert.Equal(t, domain.ErrNotFound, err)
-		assert.Nil(t, c)
-	})
-	t.Run("list all", func(t *testing.T) {
-		all, err := m.List()
-		assert.Nil(t, err)
-		assert.Equal(t, 2, len(all))
-	})
-
-	t.Run("get", func(t *testing.T) {
-		saved, err := m.Get(uID)
-		assert.Nil(t, err)
-		assert.Equal(t, u1.Title, saved.Title)
-	})
-}
-
-func Test_Update(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo)
-	u := NewFixtureBook()
-	id, err := m.Create(u)
-	assert.Nil(t, err)
-	saved, _ := m.Get(id)
-	saved.Title = "Lemmy: Biography"
-	assert.Nil(t, m.Update(saved))
-	updated, err := m.Get(id)
-	assert.Nil(t, err)
-	assert.Equal(t, "Lemmy: Biography", updated.Title)
-}
-
-func TestDelete(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo)
-	u1 := NewFixtureBook()
-	u2 := NewFixtureBook()
-	u2ID, _ := m.Create(u2)
-
-	err := m.Delete(u1.ID)
-	assert.Equal(t, domain.ErrNotFound, err)
-
-	err = m.Delete(u2ID)
-	assert.Nil(t, err)
-	_, err = m.Get(u2ID)
-	assert.Equal(t, domain.ErrNotFound, err)
-}
diff --git a/domain/entity/book/repository_inmem.go b/domain/entity/book/repository_inmem.go
deleted file mode 100644
index 1410bea..0000000
--- a/domain/entity/book/repository_inmem.go
+++ /dev/null
@@ -1,78 +0,0 @@
-package book
-
-import (
-	"strings"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-//iRepo in memory repo
-type iRepo struct {
-	m map[entity.ID]*Book
-}
-
-//NewInmemRepository create new repository
-func NewInmemRepository() *iRepo {
-	var m = map[entity.ID]*Book{}
-	return &iRepo{
-		m: m,
-	}
-}
-
-//Create a book
-func (r *iRepo) Create(e *Book) (entity.ID, error) {
-	r.m[e.ID] = e
-	return e.ID, nil
-}
-
-//Get a book
-func (r *iRepo) Get(id entity.ID) (*Book, error) {
-	if r.m[id] == nil {
-		return nil, domain.ErrNotFound
-	}
-	return r.m[id], nil
-}
-
-//Update a book
-func (r *iRepo) Update(e *Book) error {
-	_, err := r.Get(e.ID)
-	if err != nil {
-		return err
-	}
-	r.m[e.ID] = e
-	return nil
-}
-
-//Search books
-func (r *iRepo) Search(query string) ([]*Book, error) {
-	var d []*Book
-	for _, j := range r.m {
-		if strings.Contains(strings.ToLower(j.Title), query) {
-			d = append(d, j)
-		}
-	}
-	if len(d) == 0 {
-		return nil, domain.ErrNotFound
-	}
-
-	return d, nil
-}
-
-//List books
-func (r *iRepo) List() ([]*Book, error) {
-	var d []*Book
-	for _, j := range r.m {
-		d = append(d, j)
-	}
-	return d, nil
-}
-
-//Delete a book
-func (r *iRepo) Delete(id entity.ID) error {
-	if r.m[id] == nil {
-		return domain.ErrNotFound
-	}
-	r.m[id] = nil
-	return nil
-}
diff --git a/domain/entity/user/entity.go b/domain/entity/user/entity.go
deleted file mode 100644
index 5183b01..0000000
--- a/domain/entity/user/entity.go
+++ /dev/null
@@ -1,19 +0,0 @@
-package user
-
-import (
-	"time"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-//User data
-type User struct {
-	ID        entity.ID
-	Email     string
-	Password  string
-	FirstName string
-	LastName  string
-	CreatedAt time.Time
-	UpdatedAt time.Time
-	Books     []entity.ID
-}
diff --git a/domain/entity/user/fixture.go b/domain/entity/user/fixture.go
deleted file mode 100644
index 2b776c5..0000000
--- a/domain/entity/user/fixture.go
+++ /dev/null
@@ -1,18 +0,0 @@
-package user
-
-import (
-	"time"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-func NewFixtureUser() *User {
-	return &User{
-		ID:        entity.NewID(),
-		Email:     "ozzy@metalgods.net",
-		Password:  "123456",
-		FirstName: "Ozzy",
-		LastName:  "Osbourne",
-		CreatedAt: time.Now(),
-	}
-}
diff --git a/domain/entity/user/interface.go b/domain/entity/user/interface.go
deleted file mode 100644
index edecb79..0000000
--- a/domain/entity/user/interface.go
+++ /dev/null
@@ -1,28 +0,0 @@
-package user
-
-import "github.com/eminetto/clean-architecture-go-v2/domain/entity"
-
-//Reader interface
-type Reader interface {
-	Get(id entity.ID) (*User, error)
-	Search(query string) ([]*User, error)
-	List() ([]*User, error)
-}
-
-//Writer user writer
-type Writer interface {
-	Create(e *User) (entity.ID, error)
-	Update(e *User) error
-	Delete(id entity.ID) error
-}
-
-//repository interface
-type repository interface {
-	Reader
-	Writer
-}
-
-//Manager interface
-type Manager interface {
-	repository
-}
diff --git a/domain/entity/user/manager.go b/domain/entity/user/manager.go
deleted file mode 100644
index 117c16e..0000000
--- a/domain/entity/user/manager.go
+++ /dev/null
@@ -1,71 +0,0 @@
-package user
-
-import (
-	"strings"
-	"time"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-
-	"github.com/eminetto/clean-architecture-go-v2/pkg/password"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-//manager  interface
-type manager struct {
-	repo repository
-	pwd  password.Service
-}
-
-//NewManager create new repository
-func NewManager(r repository, pwd password.Service) *manager {
-	return &manager{
-		repo: r,
-		pwd:  pwd,
-	}
-}
-
-//Create an user
-func (s *manager) Create(e *User) (entity.ID, error) {
-	e.ID = entity.NewID()
-	e.CreatedAt = time.Now()
-	pwd, err := s.pwd.Generate(e.Password)
-	if err != nil {
-		return e.ID, err
-	}
-	e.Password = pwd
-	return s.repo.Create(e)
-}
-
-//Get an user
-func (s *manager) Get(id entity.ID) (*User, error) {
-	return s.repo.Get(id)
-}
-
-//Search users
-func (s *manager) Search(query string) ([]*User, error) {
-	return s.repo.Search(strings.ToLower(query))
-}
-
-//List users
-func (s *manager) List() ([]*User, error) {
-	return s.repo.List()
-}
-
-//Delete an user
-func (s *manager) Delete(id entity.ID) error {
-	u, err := s.Get(id)
-	if err != nil {
-		return err
-	}
-	if len(u.Books) > 0 {
-		return domain.ErrCannotBeDeleted
-	}
-	return s.repo.Delete(id)
-}
-
-//Update an user
-func (s *manager) Update(e *User) error {
-	e.UpdatedAt = time.Now()
-	return s.repo.Update(e)
-}
diff --git a/domain/entity/user/manager_test.go b/domain/entity/user/manager_test.go
deleted file mode 100644
index dba9b6e..0000000
--- a/domain/entity/user/manager_test.go
+++ /dev/null
@@ -1,95 +0,0 @@
-package user
-
-import (
-	"testing"
-
-	"github.com/eminetto/clean-architecture-go-v2/pkg/password"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-
-	"github.com/stretchr/testify/assert"
-)
-
-func Test_Create(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo, password.NewFakeService())
-	u := NewFixtureUser()
-	id, err := m.Create(u)
-	assert.Nil(t, err)
-	assert.Equal(t, u.ID, id)
-	assert.False(t, u.CreatedAt.IsZero())
-	assert.True(t, u.UpdatedAt.IsZero())
-}
-
-func Test_SearchAndFind(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo, password.NewFakeService())
-	u1 := NewFixtureUser()
-	u2 := NewFixtureUser()
-	u2.FirstName = "Lemmy"
-
-	uID, _ := m.Create(u1)
-	_, _ = m.Create(u2)
-
-	t.Run("search", func(t *testing.T) {
-		c, err := m.Search("ozzy")
-		assert.Nil(t, err)
-		assert.Equal(t, 1, len(c))
-		assert.Equal(t, "Osbourne", c[0].LastName)
-
-		c, err = m.Search("dio")
-		assert.Equal(t, domain.ErrNotFound, err)
-		assert.Nil(t, c)
-	})
-	t.Run("list all", func(t *testing.T) {
-		all, err := m.List()
-		assert.Nil(t, err)
-		assert.Equal(t, 2, len(all))
-	})
-
-	t.Run("get", func(t *testing.T) {
-		saved, err := m.Get(uID)
-		assert.Nil(t, err)
-		assert.Equal(t, u1.FirstName, saved.FirstName)
-	})
-}
-
-func Test_Update(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo, password.NewFakeService())
-	u := NewFixtureUser()
-	id, err := m.Create(u)
-	assert.Nil(t, err)
-	saved, _ := m.Get(id)
-	saved.FirstName = "Dio"
-	saved.Books = append(saved.Books, entity.NewID())
-	assert.Nil(t, m.Update(saved))
-	updated, err := m.Get(id)
-	assert.Nil(t, err)
-	assert.Equal(t, "Dio", updated.FirstName)
-	assert.False(t, u.UpdatedAt.IsZero())
-	assert.Equal(t, 1, len(updated.Books))
-}
-
-func TestDelete(t *testing.T) {
-	repo := NewInmemRepository()
-	m := NewManager(repo, password.NewFakeService())
-	u1 := NewFixtureUser()
-	u2 := NewFixtureUser()
-	u2ID, _ := m.Create(u2)
-
-	err := m.Delete(u1.ID)
-	assert.Equal(t, domain.ErrNotFound, err)
-
-	err = m.Delete(u2ID)
-	assert.Nil(t, err)
-	_, err = m.Get(u2ID)
-	assert.Equal(t, domain.ErrNotFound, err)
-
-	u3 := NewFixtureUser()
-	u3.Books = []entity.ID{entity.NewID()}
-	_, _ = m.Create(u3)
-	err = m.Delete(u3.ID)
-	assert.Equal(t, domain.ErrCannotBeDeleted, err)
-}
diff --git a/domain/entity/user/repository_inmem.go b/domain/entity/user/repository_inmem.go
deleted file mode 100644
index 977689e..0000000
--- a/domain/entity/user/repository_inmem.go
+++ /dev/null
@@ -1,78 +0,0 @@
-package user
-
-import (
-	"strings"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-)
-
-//IRepo in memory repo
-type IRepo struct {
-	m map[entity.ID]*User
-}
-
-//NewInmemRepository create new repository
-func NewInmemRepository() *IRepo {
-	var m = map[entity.ID]*User{}
-	return &IRepo{
-		m: m,
-	}
-}
-
-//Create an user
-func (r *IRepo) Create(e *User) (entity.ID, error) {
-	r.m[e.ID] = e
-	return e.ID, nil
-}
-
-//Get an user
-func (r *IRepo) Get(id entity.ID) (*User, error) {
-	if r.m[id] == nil {
-		return nil, domain.ErrNotFound
-	}
-	return r.m[id], nil
-}
-
-//Update an user
-func (r *IRepo) Update(e *User) error {
-	_, err := r.Get(e.ID)
-	if err != nil {
-		return err
-	}
-	r.m[e.ID] = e
-	return nil
-}
-
-//Search users
-func (r *IRepo) Search(query string) ([]*User, error) {
-	var d []*User
-	for _, j := range r.m {
-		if strings.Contains(strings.ToLower(j.FirstName), query) {
-			d = append(d, j)
-		}
-	}
-	if len(d) == 0 {
-		return nil, domain.ErrNotFound
-	}
-
-	return d, nil
-}
-
-//List users
-func (r *IRepo) List() ([]*User, error) {
-	var d []*User
-	for _, j := range r.m {
-		d = append(d, j)
-	}
-	return d, nil
-}
-
-//Delete an user
-func (r *IRepo) Delete(id entity.ID) error {
-	if r.m[id] == nil {
-		return domain.ErrNotFound
-	}
-	r.m[id] = nil
-	return nil
-}
diff --git a/domain/usecase/loan/interface.go b/domain/usecase/loan/interface.go
deleted file mode 100644
index 1ad50b2..0000000
--- a/domain/usecase/loan/interface.go
+++ /dev/null
@@ -1,12 +0,0 @@
-package loan
-
-import (
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-)
-
-//UseCase use case interface
-type UseCase interface {
-	Borrow(u *user.User, b *book.Book) error
-	Return(b *book.Book) error
-}
diff --git a/domain/usecase/loan/usecase.go b/domain/usecase/loan/usecase.go
deleted file mode 100644
index 7daa7d0..0000000
--- a/domain/usecase/loan/usecase.go
+++ /dev/null
@@ -1,100 +0,0 @@
-package loan
-
-import (
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-)
-
-type usecase struct {
-	uManager user.Manager
-	bManager book.Manager
-}
-
-//NewUseCase create new use case
-func NewUseCase(u user.Manager, b book.Manager) *usecase {
-	return &usecase{
-		uManager: u,
-		bManager: b,
-	}
-}
-
-//Borrow borrow a book to an user
-func (s *usecase) Borrow(u *user.User, b *book.Book) error {
-	u, err := s.uManager.Get(u.ID)
-	if err != nil {
-		return err
-	}
-	b, err = s.bManager.Get(b.ID)
-	if err != nil {
-		return err
-	}
-	if b.Quantity <= 0 {
-		return domain.ErrNotEnoughBooks
-	}
-	for _, v := range u.Books {
-		if v == b.ID {
-			return domain.ErrBookAlreadyBorrowed
-		}
-	}
-	u.Books = append(u.Books, b.ID)
-	err = s.uManager.Update(u)
-	if err != nil {
-		return err
-	}
-	b.Quantity--
-	err = s.bManager.Update(b)
-	if err != nil {
-		return err
-	}
-	return nil
-}
-
-//Return return a book
-func (s *usecase) Return(b *book.Book) error {
-	b, err := s.bManager.Get(b.ID)
-	if err != nil {
-		return err
-	}
-
-	all, err := s.uManager.List()
-	if err != nil {
-		return err
-	}
-	borrowed := false
-	var borrowedBy entity.ID
-	for _, u := range all {
-		for _, bookID := range u.Books {
-			if bookID == b.ID {
-				borrowed = true
-				borrowedBy = u.ID
-				break
-			}
-		}
-	}
-	if !borrowed {
-		return domain.ErrBookNotBorrowed
-	}
-	u, err := s.uManager.Get(borrowedBy)
-	if err != nil {
-		return err
-	}
-	for i, j := range u.Books {
-		if j == b.ID {
-			u.Books = append(u.Books[:i], u.Books[i+1:]...)
-			err = s.uManager.Update(u)
-			if err != nil {
-				return err
-			}
-			break
-		}
-	}
-	b.Quantity++
-	err = s.bManager.Update(b)
-	if err != nil {
-		return err
-	}
-
-	return nil
-}
diff --git a/domain/usecase/loan/usecase_test.go b/domain/usecase/loan/usecase_test.go
deleted file mode 100644
index 233b02d..0000000
--- a/domain/usecase/loan/usecase_test.go
+++ /dev/null
@@ -1,101 +0,0 @@
-package loan
-
-import (
-	"testing"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-	bmock "github.com/eminetto/clean-architecture-go-v2/domain/entity/book/mock"
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
-	umock "github.com/eminetto/clean-architecture-go-v2/domain/entity/user/mock"
-	"github.com/golang/mock/gomock"
-	"github.com/stretchr/testify/assert"
-)
-
-func Test_Borrow(t *testing.T) {
-	controller := gomock.NewController(t)
-	defer controller.Finish()
-	uMock := umock.NewMockManager(controller)
-	bMock := bmock.NewMockManager(controller)
-	uc := NewUseCase(uMock, bMock)
-	t.Run("user not found", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		uMock.EXPECT().Get(u.ID).Return(nil, domain.ErrNotFound)
-		err := uc.Borrow(u, b)
-		assert.Equal(t, domain.ErrNotFound, err)
-	})
-	t.Run("book not found", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		uMock.EXPECT().Get(u.ID).Return(u, nil)
-		bMock.EXPECT().Get(b.ID).Return(nil, domain.ErrNotFound)
-		err := uc.Borrow(u, b)
-		assert.Equal(t, domain.ErrNotFound, err)
-	})
-	t.Run("not enough books to borrow", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		b.Quantity = 0
-		uMock.EXPECT().Get(u.ID).Return(u, nil)
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		err := uc.Borrow(u, b)
-		assert.Equal(t, domain.ErrNotEnoughBooks, err)
-	})
-	t.Run("book already borrowed", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		u.Books = []entity.ID{b.ID}
-		b.Quantity = 1
-		uMock.EXPECT().Get(u.ID).Return(u, nil)
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		err := uc.Borrow(u, b)
-		assert.Equal(t, domain.ErrBookAlreadyBorrowed, err)
-	})
-	t.Run("sucess", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		uMock.EXPECT().Get(u.ID).Return(u, nil)
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		uMock.EXPECT().Update(u).Return(nil)
-		bMock.EXPECT().Update(b).Return(nil)
-		err := uc.Borrow(u, b)
-		assert.Nil(t, err)
-	})
-}
-
-func Test_Return(t *testing.T) {
-	controller := gomock.NewController(t)
-	defer controller.Finish()
-	uMock := umock.NewMockManager(controller)
-	bMock := bmock.NewMockManager(controller)
-	uc := NewUseCase(uMock, bMock)
-	t.Run("book not found", func(t *testing.T) {
-		b := book.NewFixtureBook()
-		bMock.EXPECT().Get(b.ID).Return(nil, domain.ErrNotFound)
-		err := uc.Return(b)
-		assert.Equal(t, domain.ErrNotFound, err)
-	})
-	t.Run("book not borrowed", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		uMock.EXPECT().List().Return([]*user.User{u}, nil)
-		err := uc.Return(b)
-		assert.Equal(t, domain.ErrBookNotBorrowed, err)
-	})
-	t.Run("success", func(t *testing.T) {
-		u := user.NewFixtureUser()
-		b := book.NewFixtureBook()
-		u.Books = []entity.ID{b.ID}
-		bMock.EXPECT().Get(b.ID).Return(b, nil)
-		uMock.EXPECT().Get(u.ID).Return(u, nil)
-		uMock.EXPECT().List().Return([]*user.User{u}, nil)
-		uMock.EXPECT().Update(u).Return(nil)
-		bMock.EXPECT().Update(b).Return(nil)
-		err := uc.Return(b)
-		assert.Nil(t, err)
-	})
-}
diff --git a/domain/entity/book/repository_mysql.go b/driver/repository/book_mysql.go
similarity index 72%
rename from domain/entity/book/repository_mysql.go
rename to driver/repository/book_mysql.go
index c46f051..f8ae076 100644
--- a/domain/entity/book/repository_mysql.go
+++ b/driver/repository/book_mysql.go
@@ -1,28 +1,26 @@
-package book
+package repository
 
 import (
 	"database/sql"
 	"time"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 )
 
-//mySQLRepo mysql repo
-type mySQLRepo struct {
+//BookMySQL mysql repo
+type BookMySQL struct {
 	db *sql.DB
 }
 
-//NewMySQLRepository create new repository
-func NewMySQLRepository(db *sql.DB) *mySQLRepo {
-	return &mySQLRepo{
+//NewBookMySQL create new repository
+func NewBookMySQL(db *sql.DB) *BookMySQL {
+	return &BookMySQL{
 		db: db,
 	}
 }
 
 //Create a book
-func (r *mySQLRepo) Create(e *Book) (entity.ID, error) {
+func (r *BookMySQL) Create(e *entity.Book) (entity.ID, error) {
 	stmt, err := r.db.Prepare(`
 		insert into book (id, title, author, pages, quantity, created_at) 
 		values(?,?,?,?,?,?)`)
@@ -48,12 +46,12 @@ func (r *mySQLRepo) Create(e *Book) (entity.ID, error) {
 }
 
 //Get a book
-func (r *mySQLRepo) Get(id entity.ID) (*Book, error) {
+func (r *BookMySQL) Get(id entity.ID) (*entity.Book, error) {
 	stmt, err := r.db.Prepare(`select id, title, author, pages, quantity, created_at from book where id = ?`)
 	if err != nil {
 		return nil, err
 	}
-	var b Book
+	var b entity.Book
 	rows, err := stmt.Query(id)
 	if err != nil {
 		return nil, err
@@ -65,7 +63,7 @@ func (r *mySQLRepo) Get(id entity.ID) (*Book, error) {
 }
 
 //Update a book
-func (r *mySQLRepo) Update(e *Book) error {
+func (r *BookMySQL) Update(e *entity.Book) error {
 	e.UpdatedAt = time.Now()
 	_, err := r.db.Exec("update book set title = ?, author = ?, pages = ?, quantity = ?, updated_at = ? where id = ?", e.Title, e.Author, e.Pages, e.Quantity, e.UpdatedAt.Format("2006-01-02"), e.ID)
 	if err != nil {
@@ -75,57 +73,52 @@ func (r *mySQLRepo) Update(e *Book) error {
 }
 
 //Search books
-func (r *mySQLRepo) Search(query string) ([]*Book, error) {
+func (r *BookMySQL) Search(query string) ([]*entity.Book, error) {
 	stmt, err := r.db.Prepare(`select id, title, author, pages, quantity, created_at from book where title like ?`)
 	if err != nil {
 		return nil, err
 	}
-	var books []*Book
+	var books []*entity.Book
 	rows, err := stmt.Query("%" + query + "%")
 	if err != nil {
 		return nil, err
 	}
 	for rows.Next() {
-		var b Book
+		var b entity.Book
 		err = rows.Scan(&b.ID, &b.Title, &b.Author, &b.Pages, &b.Quantity, &b.CreatedAt)
 		if err != nil {
 			return nil, err
 		}
 		books = append(books, &b)
 	}
-	if len(books) == 0 {
-		return nil, domain.ErrNotFound
-	}
+
 	return books, nil
 }
 
 //List books
-func (r *mySQLRepo) List() ([]*Book, error) {
+func (r *BookMySQL) List() ([]*entity.Book, error) {
 	stmt, err := r.db.Prepare(`select id, title, author, pages, quantity, created_at from book`)
 	if err != nil {
 		return nil, err
 	}
-	var books []*Book
+	var books []*entity.Book
 	rows, err := stmt.Query()
 	if err != nil {
 		return nil, err
 	}
 	for rows.Next() {
-		var b Book
+		var b entity.Book
 		err = rows.Scan(&b.ID, &b.Title, &b.Author, &b.Pages, &b.Quantity, &b.CreatedAt)
 		if err != nil {
 			return nil, err
 		}
 		books = append(books, &b)
 	}
-	if len(books) == 0 {
-		return nil, domain.ErrNotFound
-	}
 	return books, nil
 }
 
 //Delete a book
-func (r *mySQLRepo) Delete(id entity.ID) error {
+func (r *BookMySQL) Delete(id entity.ID) error {
 	_, err := r.db.Exec("delete from book where id = ?", id)
 	if err != nil {
 		return err
diff --git a/domain/entity/user/repository_mysql.go b/driver/repository/user_mysql.go
similarity index 78%
rename from domain/entity/user/repository_mysql.go
rename to driver/repository/user_mysql.go
index d9ac700..73cb0bb 100644
--- a/domain/entity/user/repository_mysql.go
+++ b/driver/repository/user_mysql.go
@@ -1,28 +1,27 @@
-package user
+package repository
 
 import (
 	"database/sql"
+	"fmt"
 	"time"
 
-	"github.com/eminetto/clean-architecture-go-v2/domain"
-
-	"github.com/eminetto/clean-architecture-go-v2/domain/entity"
+	"github.com/eminetto/clean-architecture-go-v2/entity"
 )
 
-//MySQLRepo mysql repo
-type MySQLRepo struct {
+//UserMySQL mysql repo
+type UserMySQL struct {
 	db *sql.DB
 }
 
-//NewMySQLRepoRepository create new repository
-func NewMySQLRepoRepository(db *sql.DB) *MySQLRepo {
-	return &MySQLRepo{
+//NewUserMySQL create new repository
+func NewUserMySQL(db *sql.DB) *UserMySQL {
+	return &UserMySQL{
 		db: db,
 	}
 }
 
 //Create an user
-func (r *MySQLRepo) Create(e *User) (entity.ID, error) {
+func (r *UserMySQL) Create(e *entity.User) (entity.ID, error) {
 	stmt, err := r.db.Prepare(`
 		insert into user (id, email, password, first_name, last_name, created_at) 
 		values(?,?,?,?,?,?)`)
@@ -48,16 +47,16 @@ func (r *MySQLRepo) Create(e *User) (entity.ID, error) {
 }
 
 //Get an user
-func (r *MySQLRepo) Get(id entity.ID) (*User, error) {
+func (r *UserMySQL) Get(id entity.ID) (*entity.User, error) {
 	return getUser(id, r.db)
 }
 
-func getUser(id entity.ID, db *sql.DB) (*User, error) {
+func getUser(id entity.ID, db *sql.DB) (*entity.User, error) {
 	stmt, err := db.Prepare(`select id, email, first_name, last_name, created_at from user where id = ?`)
 	if err != nil {
 		return nil, err
 	}
-	var u User
+	var u entity.User
 	rows, err := stmt.Query(id)
 	if err != nil {
 		return nil, err
@@ -82,7 +81,7 @@ func getUser(id entity.ID, db *sql.DB) (*User, error) {
 }
 
 //Update an user
-func (r *MySQLRepo) Update(e *User) error {
+func (r *UserMySQL) Update(e *entity.User) error {
 	e.UpdatedAt = time.Now()
 	_, err := r.db.Exec("update user set email = ?, password = ?, first_name = ?, last_name = ?, updated_at = ? where id = ?", e.Email, e.Password, e.FirstName, e.LastName, e.UpdatedAt.Format("2006-01-02"), e.ID)
 	if err != nil {
@@ -102,7 +101,7 @@ func (r *MySQLRepo) Update(e *User) error {
 }
 
 //Search users
-func (r *MySQLRepo) Search(query string) ([]*User, error) {
+func (r *UserMySQL) Search(query string) ([]*entity.User, error) {
 	stmt, err := r.db.Prepare(`select id from user where name like ?`)
 	if err != nil {
 		return nil, err
@@ -122,9 +121,9 @@ func (r *MySQLRepo) Search(query string) ([]*User, error) {
 		ids = append(ids, i)
 	}
 	if len(ids) == 0 {
-		return nil, domain.ErrNotFound
+		return nil, fmt.Errorf("not found")
 	}
-	var users []*User
+	var users []*entity.User
 	for _, id := range ids {
 		u, err := getUser(id, r.db)
 		if err != nil {
@@ -136,7 +135,7 @@ func (r *MySQLRepo) Search(query string) ([]*User, error) {
 }
 
 //List users
-func (r *MySQLRepo) List() ([]*User, error) {
+func (r *UserMySQL) List() ([]*entity.User, error) {
 	stmt, err := r.db.Prepare(`select id from user`)
 	if err != nil {
 		return nil, err
@@ -156,9 +155,9 @@ func (r *MySQLRepo) List() ([]*User, error) {
 		ids = append(ids, i)
 	}
 	if len(ids) == 0 {
-		return nil, domain.ErrNotFound
+		return nil, fmt.Errorf("not found")
 	}
-	var users []*User
+	var users []*entity.User
 	for _, id := range ids {
 		u, err := getUser(id, r.db)
 		if err != nil {
@@ -170,7 +169,7 @@ func (r *MySQLRepo) List() ([]*User, error) {
 }
 
 //Delete an user
-func (r *MySQLRepo) Delete(id entity.ID) error {
+func (r *UserMySQL) Delete(id entity.ID) error {
 	_, err := r.db.Exec("delete from user where id = ?", id)
 	if err != nil {
 		return err
diff --git a/entity/book.go b/entity/book.go
new file mode 100644
index 0000000..87b9c24
--- /dev/null
+++ b/entity/book.go
@@ -0,0 +1,41 @@
+package entity
+
+import (
+	"time"
+)
+
+//Book data
+type Book struct {
+	ID        ID
+	Title     string
+	Author    string
+	Pages     int
+	Quantity  int
+	CreatedAt time.Time
+	UpdatedAt time.Time
+}
+
+//NewBook create a new book
+func NewBook(title string, author string, pages int, quantity int) (*Book, error) {
+	b := &Book{
+		ID:        NewID(),
+		Title:     title,
+		Author:    author,
+		Pages:     pages,
+		Quantity:  quantity,
+		CreatedAt: time.Now(),
+	}
+	err := b.Validate()
+	if err != nil {
+		return nil, ErrInvalidEntity
+	}
+	return b, nil
+}
+
+//Validate validate book
+func (b *Book) Validate() error {
+	if b.Title == "" || b.Author == "" || b.Pages <= 0 || b.Quantity <= 0 {
+		return ErrInvalidEntity
+	}
+	return nil
+}
diff --git a/entity/book_test.go b/entity/book_test.go
new file mode 100644
index 0000000..a77a33d
--- /dev/null
+++ b/entity/book_test.go
@@ -0,0 +1,69 @@
+package entity_test
+
+import (
+	"testing"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewBook(t *testing.T) {
+	b, err := entity.NewBook("American Gods", "Neil Gaiman", 100, 1)
+	assert.Nil(t, err)
+	assert.Equal(t, b.Title, "American Gods")
+	assert.NotNil(t, b.ID)
+}
+
+func TestBookValidate(t *testing.T) {
+	type test struct {
+		title    string
+		author   string
+		pages    int
+		quantity int
+		want     error
+	}
+
+	tests := []test{
+		{
+			title:    "American Gods",
+			author:   "Neil Gaiman",
+			pages:    100,
+			quantity: 1,
+			want:     nil,
+		},
+		{
+			title:    "American Gods",
+			author:   "Neil Gaiman",
+			pages:    100,
+			quantity: 0,
+			want:     entity.ErrInvalidEntity,
+		},
+		{
+			title:    "",
+			author:   "Neil Gaiman",
+			pages:    100,
+			quantity: 1,
+			want:     entity.ErrInvalidEntity,
+		},
+		{
+			title:    "American Gods",
+			author:   "",
+			pages:    100,
+			quantity: 1,
+			want:     entity.ErrInvalidEntity,
+		},
+		{
+			title:    "American Gods",
+			author:   "Neil Gaiman",
+			pages:    0,
+			quantity: 1,
+			want:     entity.ErrInvalidEntity,
+		},
+	}
+	for _, tc := range tests {
+
+		_, err := entity.NewBook(tc.title, tc.author, tc.pages, tc.quantity)
+		assert.Equal(t, err, tc.want)
+	}
+
+}
diff --git a/domain/entity/entity.go b/entity/entity.go
similarity index 68%
rename from domain/entity/entity.go
rename to entity/entity.go
index 714caf8..9c99501 100644
--- a/domain/entity/entity.go
+++ b/entity/entity.go
@@ -2,15 +2,16 @@ package entity
 
 import "github.com/google/uuid"
 
+//ID entity ID
 type ID = uuid.UUID
 
+//NewID create a new entity ID
 func NewID() ID {
 	return ID(uuid.New())
 }
 
+//StringToID convert a string to an entity ID
 func StringToID(s string) (ID, error) {
 	id, err := uuid.Parse(s)
 	return ID(id), err
 }
-
-
diff --git a/domain/error.go b/entity/error.go
similarity index 82%
rename from domain/error.go
rename to entity/error.go
index e235ef3..f63c9d1 100644
--- a/domain/error.go
+++ b/entity/error.go
@@ -1,10 +1,13 @@
-package domain
+package entity
 
 import "errors"
 
 //ErrNotFound not found
 var ErrNotFound = errors.New("Not found")
 
+//ErrInvalidEntity invalid entity
+var ErrInvalidEntity = errors.New("Invalid entity")
+
 //ErrCannotBeDeleted cannot be deleted
 var ErrCannotBeDeleted = errors.New("Cannot Be Deleted")
 
diff --git a/entity/user.go b/entity/user.go
new file mode 100644
index 0000000..fbb8a9e
--- /dev/null
+++ b/entity/user.go
@@ -0,0 +1,97 @@
+package entity
+
+import (
+	"time"
+
+	"golang.org/x/crypto/bcrypt"
+)
+
+//User data
+type User struct {
+	ID        ID
+	Email     string
+	Password  string
+	FirstName string
+	LastName  string
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	Books     []ID
+}
+
+//NewUser create a new user
+func NewUser(email, password, firstName, lastName string) (*User, error) {
+	u := &User{
+		ID:        NewID(),
+		Email:     email,
+		FirstName: firstName,
+		LastName:  lastName,
+		CreatedAt: time.Now(),
+	}
+	pwd, err := generatePassword(password)
+	if err != nil {
+		return nil, err
+	}
+	u.Password = pwd
+	err = u.Validate()
+	if err != nil {
+		return nil, ErrInvalidEntity
+	}
+	return u, nil
+}
+
+//AddBook add a book
+func (u *User) AddBook(id ID) error {
+	_, err := u.GetBook(id)
+	if err == nil {
+		return ErrBookAlreadyBorrowed
+	}
+	u.Books = append(u.Books, id)
+	return nil
+}
+
+//RemoveBook remove a book
+func (u *User) RemoveBook(id ID) error {
+	for i, j := range u.Books {
+		if j == id {
+			u.Books = append(u.Books[:i], u.Books[i+1:]...)
+			return nil
+		}
+	}
+	return ErrNotFound
+}
+
+//GetBook get a book
+func (u *User) GetBook(id ID) (ID, error) {
+	for _, v := range u.Books {
+		if v == id {
+			return id, nil
+		}
+	}
+	return id, ErrNotFound
+}
+
+//Validate validate data
+func (u *User) Validate() error {
+	if u.Email == "" || u.FirstName == "" || u.LastName == "" || u.Password == "" {
+		return ErrInvalidEntity
+	}
+
+	return nil
+}
+
+//ValidatePassword validate user password
+func (u *User) ValidatePassword(p string) error {
+	err := bcrypt.CompareHashAndPassword([]byte(u.Password), []byte(p))
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func generatePassword(raw string) (string, error) {
+	hash, err := bcrypt.GenerateFromPassword([]byte(raw), 10)
+	if err != nil {
+		return "", err
+	}
+	return string(hash), nil
+}
diff --git a/entity/user_test.go b/entity/user_test.go
new file mode 100644
index 0000000..01d4f76
--- /dev/null
+++ b/entity/user_test.go
@@ -0,0 +1,111 @@
+package entity_test
+
+import (
+	"testing"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNewUser(t *testing.T) {
+	u, err := entity.NewUser("sjobs@apple.com", "new_password", "Steve", "Jobs")
+	assert.Nil(t, err)
+	assert.Equal(t, u.FirstName, "Steve")
+	assert.NotNil(t, u.ID)
+	assert.NotEqual(t, u.Password, "new_password")
+}
+
+func TestValidatePassword(t *testing.T) {
+	u, _ := entity.NewUser("sjobs@apple.com", "new_password", "Steve", "Jobs")
+	err := u.ValidatePassword("new_password")
+	assert.Nil(t, err)
+	err = u.ValidatePassword("wrong_password")
+	assert.NotNil(t, err)
+
+}
+
+func TestAddBook(t *testing.T) {
+	u, _ := entity.NewUser("sjobs@apple.com", "new_password", "Steve", "Jobs")
+	bID := entity.NewID()
+	err := u.AddBook(bID)
+	assert.Nil(t, err)
+	assert.Equal(t, 1, len(u.Books))
+	err = u.AddBook(bID)
+	assert.Equal(t, entity.ErrBookAlreadyBorrowed, err)
+
+}
+
+func TestRemoveBook(t *testing.T) {
+	u, _ := entity.NewUser("sjobs@apple.com", "new_password", "Steve", "Jobs")
+	err := u.RemoveBook(entity.NewID())
+	assert.Equal(t, entity.ErrNotFound, err)
+	bID := entity.NewID()
+	_ = u.AddBook(bID)
+	err = u.RemoveBook(bID)
+	assert.Nil(t, err)
+}
+
+func TestGetBook(t *testing.T) {
+	u, _ := entity.NewUser("sjobs@apple.com", "new_password", "Steve", "Jobs")
+	bID := entity.NewID()
+	_ = u.AddBook(bID)
+	id, err := u.GetBook(bID)
+	assert.Nil(t, err)
+	assert.Equal(t, id, bID)
+	_, err = u.GetBook(entity.NewID())
+	assert.Equal(t, entity.ErrNotFound, err)
+}
+
+func TestUserValidate(t *testing.T) {
+	type test struct {
+		email     string
+		password  string
+		firstName string
+		lastName  string
+		want      error
+	}
+
+	tests := []test{
+		{
+			email:     "sjobs@apple.com",
+			password:  "new_password",
+			firstName: "Steve",
+			lastName:  "Jobs",
+			want:      nil,
+		},
+		{
+			email:     "",
+			password:  "new_password",
+			firstName: "Steve",
+			lastName:  "Jobs",
+			want:      entity.ErrInvalidEntity,
+		},
+		{
+			email:     "sjobs@apple.com",
+			password:  "",
+			firstName: "Steve",
+			lastName:  "Jobs",
+			want:      nil,
+		},
+		{
+			email:     "sjobs@apple.com",
+			password:  "new_password",
+			firstName: "",
+			lastName:  "Jobs",
+			want:      entity.ErrInvalidEntity,
+		},
+		{
+			email:     "sjobs@apple.com",
+			password:  "new_password",
+			firstName: "Steve",
+			lastName:  "",
+			want:      entity.ErrInvalidEntity,
+		},
+	}
+	for _, tc := range tests {
+
+		_, err := entity.NewUser(tc.email, tc.password, tc.firstName, tc.lastName)
+		assert.Equal(t, err, tc.want)
+	}
+
+}
diff --git a/go.mod b/go.mod
index 36aa8a5..0faee33 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ require (
 	github.com/codegangsta/negroni v0.3.0
 	github.com/eminetto/clean-architecture-go v0.0.0-20200312132632-3195811c74a3
 	github.com/go-sql-driver/mysql v1.5.0
-	github.com/golang/mock v1.4.3
+	github.com/golang/mock v1.4.4
 	github.com/google/uuid v1.1.1
 	github.com/gorilla/context v1.1.1
 	github.com/gorilla/mux v1.6.2
@@ -17,4 +17,5 @@ require (
 	github.com/stretchr/testify v1.6.1
 	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
 	gopkg.in/mgo.v2 v2.0.0-20180705113604-9856a29383ce
+	rsc.io/quote/v3 v3.1.0 // indirect
 )
diff --git a/go.sum b/go.sum
index 23e5870..ffbed44 100644
--- a/go.sum
+++ b/go.sum
@@ -32,6 +32,8 @@ github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7a
 github.com/golang/mock v1.3.1/go.mod h1:sBzyDLLjw3U8JLTeZvSv8jJB+tU5PVekmnlKIyFUx0Y=
 github.com/golang/mock v1.4.3 h1:GV+pQPG/EUUbkh47niozDcADz6go/dUwhVzdUQHIVRw=
 github.com/golang/mock v1.4.3/go.mod h1:UOMv5ysSaYNkG+OFQykRIcU/QvvxJf3p21QfJ2Bt3cw=
+github.com/golang/mock v1.4.4 h1:l75CXGRSwbaYNpl/Z2X1XIIAMSCquvXgpVZDhwEIJsc=
+github.com/golang/mock v1.4.4/go.mod h1:l3mdAwkq5BuhzHwde/uurv3sEJeZMXNpwsxVWU71h+4=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.2/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
diff --git a/infra/init.sql b/ops/db/init.sql
similarity index 100%
rename from infra/init.sql
rename to ops/db/init.sql
diff --git a/infra/prometheus/prometheus.yml b/ops/prometheus/prometheus.yml
similarity index 100%
rename from infra/prometheus/prometheus.yml
rename to ops/prometheus/prometheus.yml
diff --git a/usecase/book/inmem.go b/usecase/book/inmem.go
new file mode 100644
index 0000000..c9c9e5e
--- /dev/null
+++ b/usecase/book/inmem.go
@@ -0,0 +1,73 @@
+package book
+
+import (
+	"strings"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//inmem in memory repo
+type inmem struct {
+	m map[entity.ID]*entity.Book
+}
+
+//newInmem create new repository
+func newInmem() *inmem {
+	var m = map[entity.ID]*entity.Book{}
+	return &inmem{
+		m: m,
+	}
+}
+
+//Create a book
+func (r *inmem) Create(e *entity.Book) (entity.ID, error) {
+	r.m[e.ID] = e
+	return e.ID, nil
+}
+
+//Get a book
+func (r *inmem) Get(id entity.ID) (*entity.Book, error) {
+	if r.m[id] == nil {
+		return nil, entity.ErrNotFound
+	}
+	return r.m[id], nil
+}
+
+//Update a book
+func (r *inmem) Update(e *entity.Book) error {
+	_, err := r.Get(e.ID)
+	if err != nil {
+		return err
+	}
+	r.m[e.ID] = e
+	return nil
+}
+
+//Search books
+func (r *inmem) Search(query string) ([]*entity.Book, error) {
+	var d []*entity.Book
+	for _, j := range r.m {
+		if strings.Contains(strings.ToLower(j.Title), query) {
+			d = append(d, j)
+		}
+	}
+	return d, nil
+}
+
+//List books
+func (r *inmem) List() ([]*entity.Book, error) {
+	var d []*entity.Book
+	for _, j := range r.m {
+		d = append(d, j)
+	}
+	return d, nil
+}
+
+//Delete a book
+func (r *inmem) Delete(id entity.ID) error {
+	if r.m[id] == nil {
+		return entity.ErrNotFound
+	}
+	r.m[id] = nil
+	return nil
+}
diff --git a/usecase/book/interface.go b/usecase/book/interface.go
new file mode 100644
index 0000000..3be17a6
--- /dev/null
+++ b/usecase/book/interface.go
@@ -0,0 +1,35 @@
+package book
+
+import (
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//Reader interface
+type Reader interface {
+	Get(id entity.ID) (*entity.Book, error)
+	Search(query string) ([]*entity.Book, error)
+	List() ([]*entity.Book, error)
+}
+
+//Writer book writer
+type Writer interface {
+	Create(e *entity.Book) (entity.ID, error)
+	Update(e *entity.Book) error
+	Delete(id entity.ID) error
+}
+
+//Repository interface
+type Repository interface {
+	Reader
+	Writer
+}
+
+//UseCase interface
+type UseCase interface {
+	GetBook(id entity.ID) (*entity.Book, error)
+	SearchBooks(query string) ([]*entity.Book, error)
+	ListBooks() ([]*entity.Book, error)
+	CreateBook(title string, author string, pages int, quantity int) (entity.ID, error)
+	UpdateBook(e *entity.Book) error
+	DeleteBook(id entity.ID) error
+}
diff --git a/domain/entity/book/mock/book.go b/usecase/book/mock/book.go
similarity index 66%
rename from domain/entity/book/mock/book.go
rename to usecase/book/mock/book.go
index e213511..86920a0 100644
--- a/domain/entity/book/mock/book.go
+++ b/usecase/book/mock/book.go
@@ -1,12 +1,11 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: domain/entity/book/interface.go
+// Source: usecase/book/interface.go
 
 // Package mock is a generated GoMock package.
 package mock
 
 import (
-	entity "github.com/eminetto/clean-architecture-go-v2/domain/entity"
-	book "github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
+	entity "github.com/eminetto/clean-architecture-go-v2/entity"
 	gomock "github.com/golang/mock/gomock"
 	reflect "reflect"
 )
@@ -35,10 +34,10 @@ func (m *MockReader) EXPECT() *MockReaderMockRecorder {
 }
 
 // Get mocks base method
-func (m *MockReader) Get(id entity.ID) (*book.Book, error) {
+func (m *MockReader) Get(id entity.ID) (*entity.Book, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Get", id)
-	ret0, _ := ret[0].(*book.Book)
+	ret0, _ := ret[0].(*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -50,10 +49,10 @@ func (mr *MockReaderMockRecorder) Get(id interface{}) *gomock.Call {
 }
 
 // Search mocks base method
-func (m *MockReader) Search(query string) ([]*book.Book, error) {
+func (m *MockReader) Search(query string) ([]*entity.Book, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Search", query)
-	ret0, _ := ret[0].([]*book.Book)
+	ret0, _ := ret[0].([]*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -65,10 +64,10 @@ func (mr *MockReaderMockRecorder) Search(query interface{}) *gomock.Call {
 }
 
 // List mocks base method
-func (m *MockReader) List() ([]*book.Book, error) {
+func (m *MockReader) List() ([]*entity.Book, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "List")
-	ret0, _ := ret[0].([]*book.Book)
+	ret0, _ := ret[0].([]*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -103,7 +102,7 @@ func (m *MockWriter) EXPECT() *MockWriterMockRecorder {
 }
 
 // Create mocks base method
-func (m *MockWriter) Create(e *book.Book) (entity.ID, error) {
+func (m *MockWriter) Create(e *entity.Book) (entity.ID, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Create", e)
 	ret0, _ := ret[0].(entity.ID)
@@ -118,7 +117,7 @@ func (mr *MockWriterMockRecorder) Create(e interface{}) *gomock.Call {
 }
 
 // Update mocks base method
-func (m *MockWriter) Update(e *book.Book) error {
+func (m *MockWriter) Update(e *entity.Book) error {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Update", e)
 	ret0, _ := ret[0].(error)
@@ -169,10 +168,10 @@ func (m *MockRepository) EXPECT() *MockRepositoryMockRecorder {
 }
 
 // Get mocks base method
-func (m *MockRepository) Get(id entity.ID) (*book.Book, error) {
+func (m *MockRepository) Get(id entity.ID) (*entity.Book, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Get", id)
-	ret0, _ := ret[0].(*book.Book)
+	ret0, _ := ret[0].(*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -184,10 +183,10 @@ func (mr *MockRepositoryMockRecorder) Get(id interface{}) *gomock.Call {
 }
 
 // Search mocks base method
-func (m *MockRepository) Search(query string) ([]*book.Book, error) {
+func (m *MockRepository) Search(query string) ([]*entity.Book, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Search", query)
-	ret0, _ := ret[0].([]*book.Book)
+	ret0, _ := ret[0].([]*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -199,10 +198,10 @@ func (mr *MockRepositoryMockRecorder) Search(query interface{}) *gomock.Call {
 }
 
 // List mocks base method
-func (m *MockRepository) List() ([]*book.Book, error) {
+func (m *MockRepository) List() ([]*entity.Book, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "List")
-	ret0, _ := ret[0].([]*book.Book)
+	ret0, _ := ret[0].([]*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -214,7 +213,7 @@ func (mr *MockRepositoryMockRecorder) List() *gomock.Call {
 }
 
 // Create mocks base method
-func (m *MockRepository) Create(e *book.Book) (entity.ID, error) {
+func (m *MockRepository) Create(e *entity.Book) (entity.ID, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Create", e)
 	ret0, _ := ret[0].(entity.ID)
@@ -229,7 +228,7 @@ func (mr *MockRepositoryMockRecorder) Create(e interface{}) *gomock.Call {
 }
 
 // Update mocks base method
-func (m *MockRepository) Update(e *book.Book) error {
+func (m *MockRepository) Update(e *entity.Book) error {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Update", e)
 	ret0, _ := ret[0].(error)
@@ -256,113 +255,113 @@ func (mr *MockRepositoryMockRecorder) Delete(id interface{}) *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Delete", reflect.TypeOf((*MockRepository)(nil).Delete), id)
 }
 
-// MockManager is a mock of Manager interface
-type MockManager struct {
+// MockUseCase is a mock of UseCase interface
+type MockUseCase struct {
 	ctrl     *gomock.Controller
-	recorder *MockManagerMockRecorder
+	recorder *MockUseCaseMockRecorder
 }
 
-// MockManagerMockRecorder is the mock recorder for MockManager
-type MockManagerMockRecorder struct {
-	mock *MockManager
+// MockUseCaseMockRecorder is the mock recorder for MockUseCase
+type MockUseCaseMockRecorder struct {
+	mock *MockUseCase
 }
 
-// NewMockManager creates a new mock instance
-func NewMockManager(ctrl *gomock.Controller) *MockManager {
-	mock := &MockManager{ctrl: ctrl}
-	mock.recorder = &MockManagerMockRecorder{mock}
+// NewMockUseCase creates a new mock instance
+func NewMockUseCase(ctrl *gomock.Controller) *MockUseCase {
+	mock := &MockUseCase{ctrl: ctrl}
+	mock.recorder = &MockUseCaseMockRecorder{mock}
 	return mock
 }
 
 // EXPECT returns an object that allows the caller to indicate expected use
-func (m *MockManager) EXPECT() *MockManagerMockRecorder {
+func (m *MockUseCase) EXPECT() *MockUseCaseMockRecorder {
 	return m.recorder
 }
 
-// Get mocks base method
-func (m *MockManager) Get(id entity.ID) (*book.Book, error) {
+// GetBook mocks base method
+func (m *MockUseCase) GetBook(id entity.ID) (*entity.Book, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Get", id)
-	ret0, _ := ret[0].(*book.Book)
+	ret := m.ctrl.Call(m, "GetBook", id)
+	ret0, _ := ret[0].(*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// Get indicates an expected call of Get
-func (mr *MockManagerMockRecorder) Get(id interface{}) *gomock.Call {
+// GetBook indicates an expected call of GetBook
+func (mr *MockUseCaseMockRecorder) GetBook(id interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Get", reflect.TypeOf((*MockManager)(nil).Get), id)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetBook", reflect.TypeOf((*MockUseCase)(nil).GetBook), id)
 }
 
-// Search mocks base method
-func (m *MockManager) Search(query string) ([]*book.Book, error) {
+// SearchBooks mocks base method
+func (m *MockUseCase) SearchBooks(query string) ([]*entity.Book, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Search", query)
-	ret0, _ := ret[0].([]*book.Book)
+	ret := m.ctrl.Call(m, "SearchBooks", query)
+	ret0, _ := ret[0].([]*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// Search indicates an expected call of Search
-func (mr *MockManagerMockRecorder) Search(query interface{}) *gomock.Call {
+// SearchBooks indicates an expected call of SearchBooks
+func (mr *MockUseCaseMockRecorder) SearchBooks(query interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Search", reflect.TypeOf((*MockManager)(nil).Search), query)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SearchBooks", reflect.TypeOf((*MockUseCase)(nil).SearchBooks), query)
 }
 
-// List mocks base method
-func (m *MockManager) List() ([]*book.Book, error) {
+// ListBooks mocks base method
+func (m *MockUseCase) ListBooks() ([]*entity.Book, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "List")
-	ret0, _ := ret[0].([]*book.Book)
+	ret := m.ctrl.Call(m, "ListBooks")
+	ret0, _ := ret[0].([]*entity.Book)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// List indicates an expected call of List
-func (mr *MockManagerMockRecorder) List() *gomock.Call {
+// ListBooks indicates an expected call of ListBooks
+func (mr *MockUseCaseMockRecorder) ListBooks() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "List", reflect.TypeOf((*MockManager)(nil).List))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ListBooks", reflect.TypeOf((*MockUseCase)(nil).ListBooks))
 }
 
-// Create mocks base method
-func (m *MockManager) Create(e *book.Book) (entity.ID, error) {
+// CreateBook mocks base method
+func (m *MockUseCase) CreateBook(title, author string, pages, quantity int) (entity.ID, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Create", e)
+	ret := m.ctrl.Call(m, "CreateBook", title, author, pages, quantity)
 	ret0, _ := ret[0].(entity.ID)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// Create indicates an expected call of Create
-func (mr *MockManagerMockRecorder) Create(e interface{}) *gomock.Call {
+// CreateBook indicates an expected call of CreateBook
+func (mr *MockUseCaseMockRecorder) CreateBook(title, author, pages, quantity interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Create", reflect.TypeOf((*MockManager)(nil).Create), e)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "CreateBook", reflect.TypeOf((*MockUseCase)(nil).CreateBook), title, author, pages, quantity)
 }
 
-// Update mocks base method
-func (m *MockManager) Update(e *book.Book) error {
+// UpdateBook mocks base method
+func (m *MockUseCase) UpdateBook(e *entity.Book) error {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Update", e)
+	ret := m.ctrl.Call(m, "UpdateBook", e)
 	ret0, _ := ret[0].(error)
 	return ret0
 }
 
-// Update indicates an expected call of Update
-func (mr *MockManagerMockRecorder) Update(e interface{}) *gomock.Call {
+// UpdateBook indicates an expected call of UpdateBook
+func (mr *MockUseCaseMockRecorder) UpdateBook(e interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Update", reflect.TypeOf((*MockManager)(nil).Update), e)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UpdateBook", reflect.TypeOf((*MockUseCase)(nil).UpdateBook), e)
 }
 
-// Delete mocks base method
-func (m *MockManager) Delete(id entity.ID) error {
+// DeleteBook mocks base method
+func (m *MockUseCase) DeleteBook(id entity.ID) error {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Delete", id)
+	ret := m.ctrl.Call(m, "DeleteBook", id)
 	ret0, _ := ret[0].(error)
 	return ret0
 }
 
-// Delete indicates an expected call of Delete
-func (mr *MockManagerMockRecorder) Delete(id interface{}) *gomock.Call {
+// DeleteBook indicates an expected call of DeleteBook
+func (mr *MockUseCaseMockRecorder) DeleteBook(id interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Delete", reflect.TypeOf((*MockManager)(nil).Delete), id)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DeleteBook", reflect.TypeOf((*MockUseCase)(nil).DeleteBook), id)
 }
diff --git a/usecase/book/service.go b/usecase/book/service.go
new file mode 100644
index 0000000..a0ebb4e
--- /dev/null
+++ b/usecase/book/service.go
@@ -0,0 +1,85 @@
+package book
+
+import (
+	"strings"
+	"time"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//Service book usecase
+type Service struct {
+	repo Repository
+}
+
+//NewService create new service
+func NewService(r Repository) *Service {
+	return &Service{
+		repo: r,
+	}
+}
+
+//CreateBook create a book
+func (s *Service) CreateBook(title string, author string, pages int, quantity int) (entity.ID, error) {
+	b, err := entity.NewBook(title, author, pages, quantity)
+	if err != nil {
+		return b.ID, err
+	}
+	return s.repo.Create(b)
+}
+
+//GetBook get a book
+func (s *Service) GetBook(id entity.ID) (*entity.Book, error) {
+	b, err := s.repo.Get(id)
+	if b == nil {
+		return nil, entity.ErrNotFound
+	}
+	if err != nil {
+		return nil, err
+	}
+
+	return b, nil
+}
+
+//SearchBooks search books
+func (s *Service) SearchBooks(query string) ([]*entity.Book, error) {
+	books, err := s.repo.Search(strings.ToLower(query))
+	if err != nil {
+		return nil, err
+	}
+	if len(books) == 0 {
+		return nil, entity.ErrNotFound
+	}
+	return books, nil
+}
+
+//ListBooks list books
+func (s *Service) ListBooks() ([]*entity.Book, error) {
+	books, err := s.repo.List()
+	if err != nil {
+		return nil, err
+	}
+	if len(books) == 0 {
+		return nil, entity.ErrNotFound
+	}
+	return books, nil
+}
+
+//DeleteBook Delete a book
+func (s *Service) DeleteBook(id entity.ID) error {
+	_, err := s.GetBook(id)
+	if err != nil {
+		return err
+	}
+	return s.repo.Delete(id)
+}
+
+//UpdateBook Update a book
+func (s *Service) UpdateBook(e *entity.Book) error {
+	err := e.Validate()
+	if err != nil {
+		return err
+	}
+	e.UpdatedAt = time.Now()
+	return s.repo.Update(e)
+}
diff --git a/usecase/book/service_test.go b/usecase/book/service_test.go
new file mode 100644
index 0000000..999b5b6
--- /dev/null
+++ b/usecase/book/service_test.go
@@ -0,0 +1,92 @@
+package book
+
+import (
+	"testing"
+	"time"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func newFixtureBook() *entity.Book {
+	return &entity.Book{
+		Title:     "I Am Ozzy",
+		Author:    "Ozzy Osbourne",
+		Pages:     294,
+		Quantity:  1,
+		CreatedAt: time.Now(),
+	}
+}
+
+func Test_Create(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u := newFixtureBook()
+	_, err := m.CreateBook(u.Title, u.Author, u.Pages, u.Quantity)
+	assert.Nil(t, err)
+	assert.False(t, u.CreatedAt.IsZero())
+}
+
+func Test_SearchAndFind(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u1 := newFixtureBook()
+	u2 := newFixtureBook()
+	u2.Title = "Lemmy: Biography"
+
+	uID, _ := m.CreateBook(u1.Title, u1.Author, u1.Pages, u1.Quantity)
+	_, _ = m.CreateBook(u2.Title, u2.Author, u2.Pages, u2.Quantity)
+
+	t.Run("search", func(t *testing.T) {
+		c, err := m.SearchBooks("ozzy")
+		assert.Nil(t, err)
+		assert.Equal(t, 1, len(c))
+		assert.Equal(t, "I Am Ozzy", c[0].Title)
+
+		c, err = m.SearchBooks("dio")
+		assert.Equal(t, entity.ErrNotFound, err)
+		assert.Nil(t, c)
+	})
+	t.Run("list all", func(t *testing.T) {
+		all, err := m.ListBooks()
+		assert.Nil(t, err)
+		assert.Equal(t, 2, len(all))
+	})
+
+	t.Run("get", func(t *testing.T) {
+		saved, err := m.GetBook(uID)
+		assert.Nil(t, err)
+		assert.Equal(t, u1.Title, saved.Title)
+	})
+}
+
+func Test_Update(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u := newFixtureBook()
+	id, err := m.CreateBook(u.Title, u.Author, u.Pages, u.Quantity)
+	assert.Nil(t, err)
+	saved, _ := m.GetBook(id)
+	saved.Title = "Lemmy: Biography"
+	assert.Nil(t, m.UpdateBook(saved))
+	updated, err := m.GetBook(id)
+	assert.Nil(t, err)
+	assert.Equal(t, "Lemmy: Biography", updated.Title)
+}
+
+func TestDelete(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u1 := newFixtureBook()
+	u2 := newFixtureBook()
+	u2ID, _ := m.CreateBook(u2.Title, u2.Author, u2.Pages, u2.Quantity)
+
+	err := m.DeleteBook(u1.ID)
+	assert.Equal(t, entity.ErrNotFound, err)
+
+	err = m.DeleteBook(u2ID)
+	assert.Nil(t, err)
+	_, err = m.GetBook(u2ID)
+	assert.Equal(t, entity.ErrNotFound, err)
+}
diff --git a/usecase/loan/interface.go b/usecase/loan/interface.go
new file mode 100644
index 0000000..802a6ef
--- /dev/null
+++ b/usecase/loan/interface.go
@@ -0,0 +1,11 @@
+package loan
+
+import (
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//UseCase use case interface
+type UseCase interface {
+	Borrow(u *entity.User, b *entity.Book) error
+	Return(b *entity.Book) error
+}
diff --git a/domain/usecase/loan/mock/loan.go b/usecase/loan/mock/loan.go
similarity index 83%
rename from domain/usecase/loan/mock/loan.go
rename to usecase/loan/mock/loan.go
index ce46511..d3518a0 100644
--- a/domain/usecase/loan/mock/loan.go
+++ b/usecase/loan/mock/loan.go
@@ -1,12 +1,11 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: domain/usecase/loan/interface.go
+// Source: usecase/loan/interface.go
 
 // Package mock is a generated GoMock package.
 package mock
 
 import (
-	book "github.com/eminetto/clean-architecture-go-v2/domain/entity/book"
-	user "github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
+	entity "github.com/eminetto/clean-architecture-go-v2/entity"
 	gomock "github.com/golang/mock/gomock"
 	reflect "reflect"
 )
@@ -35,7 +34,7 @@ func (m *MockUseCase) EXPECT() *MockUseCaseMockRecorder {
 }
 
 // Borrow mocks base method
-func (m *MockUseCase) Borrow(u *user.User, b *book.Book) error {
+func (m *MockUseCase) Borrow(u *entity.User, b *entity.Book) error {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Borrow", u, b)
 	ret0, _ := ret[0].(error)
@@ -49,7 +48,7 @@ func (mr *MockUseCaseMockRecorder) Borrow(u, b interface{}) *gomock.Call {
 }
 
 // Return mocks base method
-func (m *MockUseCase) Return(b *book.Book) error {
+func (m *MockUseCase) Return(b *entity.Book) error {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Return", b)
 	ret0, _ := ret[0].(error)
diff --git a/usecase/loan/service.go b/usecase/loan/service.go
new file mode 100644
index 0000000..7516333
--- /dev/null
+++ b/usecase/loan/service.go
@@ -0,0 +1,97 @@
+package loan
+
+import (
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/book"
+	"github.com/eminetto/clean-architecture-go-v2/usecase/user"
+)
+
+//Service loan usecase
+type Service struct {
+	userService user.UseCase
+	bookService book.UseCase
+}
+
+//NewService create new use case
+func NewService(u user.UseCase, b book.UseCase) *Service {
+	return &Service{
+		userService: u,
+		bookService: b,
+	}
+}
+
+//Borrow borrow a book to an user
+func (s *Service) Borrow(u *entity.User, b *entity.Book) error {
+	u, err := s.userService.GetUser(u.ID)
+	if err != nil {
+		return err
+	}
+	b, err = s.bookService.GetBook(b.ID)
+	if err != nil {
+		return err
+	}
+	if b.Quantity <= 0 {
+		return entity.ErrNotEnoughBooks
+	}
+
+	err = u.AddBook(b.ID)
+	if err != nil {
+		return err
+	}
+	err = s.userService.UpdateUser(u)
+	if err != nil {
+		return err
+	}
+	b.Quantity--
+	err = s.bookService.UpdateBook(b)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+//Return return a book
+func (s *Service) Return(b *entity.Book) error {
+	b, err := s.bookService.GetBook(b.ID)
+	if err != nil {
+		return err
+	}
+
+	all, err := s.userService.ListUsers()
+	if err != nil {
+		return err
+	}
+	borrowed := false
+	var borrowedBy entity.ID
+	for _, u := range all {
+		_, err := u.GetBook(b.ID)
+		if err != nil {
+			continue
+		}
+		borrowed = true
+		borrowedBy = u.ID
+		break
+	}
+	if !borrowed {
+		return entity.ErrBookNotBorrowed
+	}
+	u, err := s.userService.GetUser(borrowedBy)
+	if err != nil {
+		return err
+	}
+	err = u.RemoveBook(b.ID)
+	if err != nil {
+		return err
+	}
+	err = s.userService.UpdateUser(u)
+	if err != nil {
+		return err
+	}
+	b.Quantity++
+	err = s.bookService.UpdateBook(b)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
diff --git a/usecase/loan/service_test.go b/usecase/loan/service_test.go
new file mode 100644
index 0000000..68f30fd
--- /dev/null
+++ b/usecase/loan/service_test.go
@@ -0,0 +1,129 @@
+package loan
+
+import (
+	"testing"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+
+	bmock "github.com/eminetto/clean-architecture-go-v2/usecase/book/mock"
+	umock "github.com/eminetto/clean-architecture-go-v2/usecase/user/mock"
+	"github.com/golang/mock/gomock"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Borrow(t *testing.T) {
+	controller := gomock.NewController(t)
+	defer controller.Finish()
+	uMock := umock.NewMockUseCase(controller)
+	bMock := bmock.NewMockUseCase(controller)
+	uc := NewService(uMock, bMock)
+	t.Run("user not found", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		uMock.EXPECT().GetUser(u.ID).Return(nil, entity.ErrNotFound)
+		err := uc.Borrow(u, b)
+		assert.Equal(t, entity.ErrNotFound, err)
+	})
+	t.Run("book not found", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		uMock.EXPECT().GetUser(u.ID).Return(u, nil)
+		bMock.EXPECT().GetBook(b.ID).Return(nil, entity.ErrNotFound)
+		err := uc.Borrow(u, b)
+		assert.Equal(t, entity.ErrNotFound, err)
+	})
+	t.Run("not enough books to borrow", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		b.Quantity = 0
+		uMock.EXPECT().GetUser(u.ID).Return(u, nil)
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		err := uc.Borrow(u, b)
+		assert.Equal(t, entity.ErrNotEnoughBooks, err)
+	})
+	t.Run("book already borrowed", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		u.AddBook(b.ID)
+		b.Quantity = 1
+		uMock.EXPECT().GetUser(u.ID).Return(u, nil)
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		err := uc.Borrow(u, b)
+		assert.Equal(t, entity.ErrBookAlreadyBorrowed, err)
+	})
+	t.Run("sucess", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID:       entity.NewID(),
+			Quantity: 10,
+		}
+		uMock.EXPECT().GetUser(u.ID).Return(u, nil)
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		uMock.EXPECT().UpdateUser(u).Return(nil)
+		bMock.EXPECT().UpdateBook(b).Return(nil)
+		err := uc.Borrow(u, b)
+		assert.Nil(t, err)
+	})
+}
+
+func Test_Return(t *testing.T) {
+	controller := gomock.NewController(t)
+	defer controller.Finish()
+	uMock := umock.NewMockUseCase(controller)
+	bMock := bmock.NewMockUseCase(controller)
+	uc := NewService(uMock, bMock)
+	t.Run("book not found", func(t *testing.T) {
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		bMock.EXPECT().GetBook(b.ID).Return(nil, entity.ErrNotFound)
+		err := uc.Return(b)
+		assert.Equal(t, entity.ErrNotFound, err)
+	})
+	t.Run("book not borrowed", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		uMock.EXPECT().ListUsers().Return([]*entity.User{u}, nil)
+		err := uc.Return(b)
+		assert.Equal(t, entity.ErrBookNotBorrowed, err)
+	})
+	t.Run("success", func(t *testing.T) {
+		u := &entity.User{
+			ID: entity.NewID(),
+		}
+		b := &entity.Book{
+			ID: entity.NewID(),
+		}
+		u.AddBook(b.ID)
+		bMock.EXPECT().GetBook(b.ID).Return(b, nil)
+		uMock.EXPECT().GetUser(u.ID).Return(u, nil)
+		uMock.EXPECT().ListUsers().Return([]*entity.User{u}, nil)
+		uMock.EXPECT().UpdateUser(u).Return(nil)
+		bMock.EXPECT().UpdateBook(b).Return(nil)
+		err := uc.Return(b)
+		assert.Nil(t, err)
+	})
+}
diff --git a/usecase/user/inmem.go b/usecase/user/inmem.go
new file mode 100644
index 0000000..651c6d4
--- /dev/null
+++ b/usecase/user/inmem.go
@@ -0,0 +1,78 @@
+package user
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//inmem in memory repo
+type inmem struct {
+	m map[entity.ID]*entity.User
+}
+
+//newInmem create new repository
+func newInmem() *inmem {
+	var m = map[entity.ID]*entity.User{}
+	return &inmem{
+		m: m,
+	}
+}
+
+//Create an user
+func (r *inmem) Create(e *entity.User) (entity.ID, error) {
+	r.m[e.ID] = e
+	return e.ID, nil
+}
+
+//Get an user
+func (r *inmem) Get(id entity.ID) (*entity.User, error) {
+	if r.m[id] == nil {
+		return nil, entity.ErrNotFound
+	}
+	return r.m[id], nil
+}
+
+//Update an user
+func (r *inmem) Update(e *entity.User) error {
+	_, err := r.Get(e.ID)
+	if err != nil {
+		return err
+	}
+	r.m[e.ID] = e
+	return nil
+}
+
+//Search users
+func (r *inmem) Search(query string) ([]*entity.User, error) {
+	var d []*entity.User
+	for _, j := range r.m {
+		if strings.Contains(strings.ToLower(j.FirstName), query) {
+			d = append(d, j)
+		}
+	}
+	if len(d) == 0 {
+		return nil, entity.ErrNotFound
+	}
+
+	return d, nil
+}
+
+//List users
+func (r *inmem) List() ([]*entity.User, error) {
+	var d []*entity.User
+	for _, j := range r.m {
+		d = append(d, j)
+	}
+	return d, nil
+}
+
+//Delete an user
+func (r *inmem) Delete(id entity.ID) error {
+	if r.m[id] == nil {
+		return fmt.Errorf("not found")
+	}
+	r.m[id] = nil
+	return nil
+}
diff --git a/usecase/user/interface.go b/usecase/user/interface.go
new file mode 100644
index 0000000..340205a
--- /dev/null
+++ b/usecase/user/interface.go
@@ -0,0 +1,35 @@
+package user
+
+import (
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//Reader interface
+type Reader interface {
+	Get(id entity.ID) (*entity.User, error)
+	Search(query string) ([]*entity.User, error)
+	List() ([]*entity.User, error)
+}
+
+//Writer user writer
+type Writer interface {
+	Create(e *entity.User) (entity.ID, error)
+	Update(e *entity.User) error
+	Delete(id entity.ID) error
+}
+
+//Repository interface
+type Repository interface {
+	Reader
+	Writer
+}
+
+//UseCase interface
+type UseCase interface {
+	GetUser(id entity.ID) (*entity.User, error)
+	SearchUsers(query string) ([]*entity.User, error)
+	ListUsers() ([]*entity.User, error)
+	CreateUser(email, password, firstName, lastName string) (entity.ID, error)
+	UpdateUser(e *entity.User) error
+	DeleteUser(id entity.ID) error
+}
diff --git a/domain/entity/user/mock/user.go b/usecase/user/mock/user.go
similarity index 65%
rename from domain/entity/user/mock/user.go
rename to usecase/user/mock/user.go
index 506b675..3a8e2df 100644
--- a/domain/entity/user/mock/user.go
+++ b/usecase/user/mock/user.go
@@ -1,12 +1,11 @@
 // Code generated by MockGen. DO NOT EDIT.
-// Source: domain/entity/user/interface.go
+// Source: usecase/user/interface.go
 
 // Package mock is a generated GoMock package.
 package mock
 
 import (
-	entity "github.com/eminetto/clean-architecture-go-v2/domain/entity"
-	user "github.com/eminetto/clean-architecture-go-v2/domain/entity/user"
+	entity "github.com/eminetto/clean-architecture-go-v2/entity"
 	gomock "github.com/golang/mock/gomock"
 	reflect "reflect"
 )
@@ -35,10 +34,10 @@ func (m *MockReader) EXPECT() *MockReaderMockRecorder {
 }
 
 // Get mocks base method
-func (m *MockReader) Get(id entity.ID) (*user.User, error) {
+func (m *MockReader) Get(id entity.ID) (*entity.User, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Get", id)
-	ret0, _ := ret[0].(*user.User)
+	ret0, _ := ret[0].(*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -50,10 +49,10 @@ func (mr *MockReaderMockRecorder) Get(id interface{}) *gomock.Call {
 }
 
 // Search mocks base method
-func (m *MockReader) Search(query string) ([]*user.User, error) {
+func (m *MockReader) Search(query string) ([]*entity.User, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Search", query)
-	ret0, _ := ret[0].([]*user.User)
+	ret0, _ := ret[0].([]*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -65,10 +64,10 @@ func (mr *MockReaderMockRecorder) Search(query interface{}) *gomock.Call {
 }
 
 // List mocks base method
-func (m *MockReader) List() ([]*user.User, error) {
+func (m *MockReader) List() ([]*entity.User, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "List")
-	ret0, _ := ret[0].([]*user.User)
+	ret0, _ := ret[0].([]*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -103,7 +102,7 @@ func (m *MockWriter) EXPECT() *MockWriterMockRecorder {
 }
 
 // Create mocks base method
-func (m *MockWriter) Create(e *user.User) (entity.ID, error) {
+func (m *MockWriter) Create(e *entity.User) (entity.ID, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Create", e)
 	ret0, _ := ret[0].(entity.ID)
@@ -118,7 +117,7 @@ func (mr *MockWriterMockRecorder) Create(e interface{}) *gomock.Call {
 }
 
 // Update mocks base method
-func (m *MockWriter) Update(e *user.User) error {
+func (m *MockWriter) Update(e *entity.User) error {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Update", e)
 	ret0, _ := ret[0].(error)
@@ -169,10 +168,10 @@ func (m *MockRepository) EXPECT() *MockRepositoryMockRecorder {
 }
 
 // Get mocks base method
-func (m *MockRepository) Get(id entity.ID) (*user.User, error) {
+func (m *MockRepository) Get(id entity.ID) (*entity.User, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Get", id)
-	ret0, _ := ret[0].(*user.User)
+	ret0, _ := ret[0].(*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -184,10 +183,10 @@ func (mr *MockRepositoryMockRecorder) Get(id interface{}) *gomock.Call {
 }
 
 // Search mocks base method
-func (m *MockRepository) Search(query string) ([]*user.User, error) {
+func (m *MockRepository) Search(query string) ([]*entity.User, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Search", query)
-	ret0, _ := ret[0].([]*user.User)
+	ret0, _ := ret[0].([]*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -199,10 +198,10 @@ func (mr *MockRepositoryMockRecorder) Search(query interface{}) *gomock.Call {
 }
 
 // List mocks base method
-func (m *MockRepository) List() ([]*user.User, error) {
+func (m *MockRepository) List() ([]*entity.User, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "List")
-	ret0, _ := ret[0].([]*user.User)
+	ret0, _ := ret[0].([]*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
@@ -214,7 +213,7 @@ func (mr *MockRepositoryMockRecorder) List() *gomock.Call {
 }
 
 // Create mocks base method
-func (m *MockRepository) Create(e *user.User) (entity.ID, error) {
+func (m *MockRepository) Create(e *entity.User) (entity.ID, error) {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Create", e)
 	ret0, _ := ret[0].(entity.ID)
@@ -229,7 +228,7 @@ func (mr *MockRepositoryMockRecorder) Create(e interface{}) *gomock.Call {
 }
 
 // Update mocks base method
-func (m *MockRepository) Update(e *user.User) error {
+func (m *MockRepository) Update(e *entity.User) error {
 	m.ctrl.T.Helper()
 	ret := m.ctrl.Call(m, "Update", e)
 	ret0, _ := ret[0].(error)
@@ -256,113 +255,113 @@ func (mr *MockRepositoryMockRecorder) Delete(id interface{}) *gomock.Call {
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Delete", reflect.TypeOf((*MockRepository)(nil).Delete), id)
 }
 
-// MockManager is a mock of Manager interface
-type MockManager struct {
+// MockUseCase is a mock of UseCase interface
+type MockUseCase struct {
 	ctrl     *gomock.Controller
-	recorder *MockManagerMockRecorder
+	recorder *MockUseCaseMockRecorder
 }
 
-// MockManagerMockRecorder is the mock recorder for MockManager
-type MockManagerMockRecorder struct {
-	mock *MockManager
+// MockUseCaseMockRecorder is the mock recorder for MockUseCase
+type MockUseCaseMockRecorder struct {
+	mock *MockUseCase
 }
 
-// NewMockManager creates a new mock instance
-func NewMockManager(ctrl *gomock.Controller) *MockManager {
-	mock := &MockManager{ctrl: ctrl}
-	mock.recorder = &MockManagerMockRecorder{mock}
+// NewMockUseCase creates a new mock instance
+func NewMockUseCase(ctrl *gomock.Controller) *MockUseCase {
+	mock := &MockUseCase{ctrl: ctrl}
+	mock.recorder = &MockUseCaseMockRecorder{mock}
 	return mock
 }
 
 // EXPECT returns an object that allows the caller to indicate expected use
-func (m *MockManager) EXPECT() *MockManagerMockRecorder {
+func (m *MockUseCase) EXPECT() *MockUseCaseMockRecorder {
 	return m.recorder
 }
 
-// Get mocks base method
-func (m *MockManager) Get(id entity.ID) (*user.User, error) {
+// GetUser mocks base method
+func (m *MockUseCase) GetUser(id entity.ID) (*entity.User, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Get", id)
-	ret0, _ := ret[0].(*user.User)
+	ret := m.ctrl.Call(m, "GetUser", id)
+	ret0, _ := ret[0].(*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// Get indicates an expected call of Get
-func (mr *MockManagerMockRecorder) Get(id interface{}) *gomock.Call {
+// GetUser indicates an expected call of GetUser
+func (mr *MockUseCaseMockRecorder) GetUser(id interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Get", reflect.TypeOf((*MockManager)(nil).Get), id)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "GetUser", reflect.TypeOf((*MockUseCase)(nil).GetUser), id)
 }
 
-// Search mocks base method
-func (m *MockManager) Search(query string) ([]*user.User, error) {
+// SearchUsers mocks base method
+func (m *MockUseCase) SearchUsers(query string) ([]*entity.User, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Search", query)
-	ret0, _ := ret[0].([]*user.User)
+	ret := m.ctrl.Call(m, "SearchUsers", query)
+	ret0, _ := ret[0].([]*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// Search indicates an expected call of Search
-func (mr *MockManagerMockRecorder) Search(query interface{}) *gomock.Call {
+// SearchUsers indicates an expected call of SearchUsers
+func (mr *MockUseCaseMockRecorder) SearchUsers(query interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Search", reflect.TypeOf((*MockManager)(nil).Search), query)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "SearchUsers", reflect.TypeOf((*MockUseCase)(nil).SearchUsers), query)
 }
 
-// List mocks base method
-func (m *MockManager) List() ([]*user.User, error) {
+// ListUsers mocks base method
+func (m *MockUseCase) ListUsers() ([]*entity.User, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "List")
-	ret0, _ := ret[0].([]*user.User)
+	ret := m.ctrl.Call(m, "ListUsers")
+	ret0, _ := ret[0].([]*entity.User)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// List indicates an expected call of List
-func (mr *MockManagerMockRecorder) List() *gomock.Call {
+// ListUsers indicates an expected call of ListUsers
+func (mr *MockUseCaseMockRecorder) ListUsers() *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "List", reflect.TypeOf((*MockManager)(nil).List))
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ListUsers", reflect.TypeOf((*MockUseCase)(nil).ListUsers))
 }
 
-// Create mocks base method
-func (m *MockManager) Create(e *user.User) (entity.ID, error) {
+// CreateUser mocks base method
+func (m *MockUseCase) CreateUser(email, password, firstName, lastName string) (entity.ID, error) {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Create", e)
+	ret := m.ctrl.Call(m, "CreateUser", email, password, firstName, lastName)
 	ret0, _ := ret[0].(entity.ID)
 	ret1, _ := ret[1].(error)
 	return ret0, ret1
 }
 
-// Create indicates an expected call of Create
-func (mr *MockManagerMockRecorder) Create(e interface{}) *gomock.Call {
+// CreateUser indicates an expected call of CreateUser
+func (mr *MockUseCaseMockRecorder) CreateUser(email, password, firstName, lastName interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Create", reflect.TypeOf((*MockManager)(nil).Create), e)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "CreateUser", reflect.TypeOf((*MockUseCase)(nil).CreateUser), email, password, firstName, lastName)
 }
 
-// Update mocks base method
-func (m *MockManager) Update(e *user.User) error {
+// UpdateUser mocks base method
+func (m *MockUseCase) UpdateUser(e *entity.User) error {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Update", e)
+	ret := m.ctrl.Call(m, "UpdateUser", e)
 	ret0, _ := ret[0].(error)
 	return ret0
 }
 
-// Update indicates an expected call of Update
-func (mr *MockManagerMockRecorder) Update(e interface{}) *gomock.Call {
+// UpdateUser indicates an expected call of UpdateUser
+func (mr *MockUseCaseMockRecorder) UpdateUser(e interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Update", reflect.TypeOf((*MockManager)(nil).Update), e)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "UpdateUser", reflect.TypeOf((*MockUseCase)(nil).UpdateUser), e)
 }
 
-// Delete mocks base method
-func (m *MockManager) Delete(id entity.ID) error {
+// DeleteUser mocks base method
+func (m *MockUseCase) DeleteUser(id entity.ID) error {
 	m.ctrl.T.Helper()
-	ret := m.ctrl.Call(m, "Delete", id)
+	ret := m.ctrl.Call(m, "DeleteUser", id)
 	ret0, _ := ret[0].(error)
 	return ret0
 }
 
-// Delete indicates an expected call of Delete
-func (mr *MockManagerMockRecorder) Delete(id interface{}) *gomock.Call {
+// DeleteUser indicates an expected call of DeleteUser
+func (mr *MockUseCaseMockRecorder) DeleteUser(id interface{}) *gomock.Call {
 	mr.mock.ctrl.T.Helper()
-	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Delete", reflect.TypeOf((*MockManager)(nil).Delete), id)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "DeleteUser", reflect.TypeOf((*MockUseCase)(nil).DeleteUser), id)
 }
diff --git a/usecase/user/service.go b/usecase/user/service.go
new file mode 100644
index 0000000..2f257b9
--- /dev/null
+++ b/usecase/user/service.go
@@ -0,0 +1,69 @@
+package user
+
+import (
+	"strings"
+	"time"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+)
+
+//Service  interface
+type Service struct {
+	repo Repository
+}
+
+//NewService create new use case
+func NewService(r Repository) *Service {
+	return &Service{
+		repo: r,
+	}
+}
+
+//CreateUser Create an user
+func (s *Service) CreateUser(email, password, firstName, lastName string) (entity.ID, error) {
+	e, err := entity.NewUser(email, password, firstName, lastName)
+	if err != nil {
+		return e.ID, err
+	}
+	return s.repo.Create(e)
+}
+
+//GetUser Get an user
+func (s *Service) GetUser(id entity.ID) (*entity.User, error) {
+	return s.repo.Get(id)
+}
+
+//SearchUsers Search users
+func (s *Service) SearchUsers(query string) ([]*entity.User, error) {
+	return s.repo.Search(strings.ToLower(query))
+}
+
+//ListUsers List users
+func (s *Service) ListUsers() ([]*entity.User, error) {
+	return s.repo.List()
+}
+
+//DeleteUser Delete an user
+func (s *Service) DeleteUser(id entity.ID) error {
+	u, err := s.GetUser(id)
+	if u == nil {
+		return entity.ErrNotFound
+	}
+	if err != nil {
+		return err
+	}
+	if len(u.Books) > 0 {
+		return entity.ErrCannotBeDeleted
+	}
+	return s.repo.Delete(id)
+}
+
+//UpdateUser Update an user
+func (s *Service) UpdateUser(e *entity.User) error {
+	err := e.Validate()
+	if err != nil {
+		return entity.ErrInvalidEntity
+	}
+	e.UpdatedAt = time.Now()
+	return s.repo.Update(e)
+}
diff --git a/usecase/user/service_test.go b/usecase/user/service_test.go
new file mode 100644
index 0000000..99fafc4
--- /dev/null
+++ b/usecase/user/service_test.go
@@ -0,0 +1,105 @@
+package user
+
+import (
+	"testing"
+	"time"
+
+	"github.com/eminetto/clean-architecture-go-v2/entity"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func newFixtureUser() *entity.User {
+	return &entity.User{
+		ID:        entity.NewID(),
+		Email:     "ozzy@metalgods.net",
+		Password:  "123456",
+		FirstName: "Ozzy",
+		LastName:  "Osbourne",
+		CreatedAt: time.Now(),
+	}
+}
+
+func Test_Create(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u := newFixtureUser()
+	_, err := m.CreateUser(u.Email, u.Password, u.FirstName, u.LastName)
+	assert.Nil(t, err)
+	assert.False(t, u.CreatedAt.IsZero())
+	assert.True(t, u.UpdatedAt.IsZero())
+}
+
+func Test_SearchAndFind(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u1 := newFixtureUser()
+	u2 := newFixtureUser()
+	u2.FirstName = "Lemmy"
+
+	uID, _ := m.CreateUser(u1.Email, u1.Password, u1.FirstName, u1.LastName)
+	_, _ = m.CreateUser(u2.Email, u2.Password, u2.FirstName, u2.LastName)
+
+	t.Run("search", func(t *testing.T) {
+		c, err := m.SearchUsers("ozzy")
+		assert.Nil(t, err)
+		assert.Equal(t, 1, len(c))
+		assert.Equal(t, "Osbourne", c[0].LastName)
+
+		c, err = m.SearchUsers("dio")
+		assert.Equal(t, entity.ErrNotFound, err)
+		assert.Nil(t, c)
+	})
+	t.Run("list all", func(t *testing.T) {
+		all, err := m.ListUsers()
+		assert.Nil(t, err)
+		assert.Equal(t, 2, len(all))
+	})
+
+	t.Run("get", func(t *testing.T) {
+		saved, err := m.GetUser(uID)
+		assert.Nil(t, err)
+		assert.Equal(t, u1.FirstName, saved.FirstName)
+	})
+}
+
+func Test_Update(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u := newFixtureUser()
+	id, err := m.CreateUser(u.Email, u.Password, u.FirstName, u.LastName)
+	assert.Nil(t, err)
+	saved, _ := m.GetUser(id)
+	saved.FirstName = "Dio"
+	saved.Books = append(saved.Books, entity.NewID())
+	assert.Nil(t, m.UpdateUser(saved))
+	updated, err := m.GetUser(id)
+	assert.Nil(t, err)
+	assert.Equal(t, "Dio", updated.FirstName)
+	assert.False(t, updated.UpdatedAt.IsZero())
+	assert.Equal(t, 1, len(updated.Books))
+}
+
+func TestDelete(t *testing.T) {
+	repo := newInmem()
+	m := NewService(repo)
+	u1 := newFixtureUser()
+	u2 := newFixtureUser()
+	u2ID, _ := m.CreateUser(u2.Email, u2.Password, u2.FirstName, u2.LastName)
+
+	err := m.DeleteUser(u1.ID)
+	assert.Equal(t, entity.ErrNotFound, err)
+
+	err = m.DeleteUser(u2ID)
+	assert.Nil(t, err)
+	_, err = m.GetUser(u2ID)
+	assert.Equal(t, entity.ErrNotFound, err)
+
+	u3 := newFixtureUser()
+	id, _ := m.CreateUser(u3.Email, u3.Password, u3.FirstName, u3.LastName)
+	saved, _ := m.GetUser(id)
+	saved.Books = []entity.ID{entity.NewID()}
+	_ = m.UpdateUser(saved)
+	err = m.DeleteUser(id)
+	assert.Equal(t, entity.ErrCannotBeDeleted, err)
+}