diff --git a/apps/users/src/app/app.module.ts b/apps/users/src/app/app.module.ts
index bc5de0c..31f1953 100644
--- a/apps/users/src/app/app.module.ts
+++ b/apps/users/src/app/app.module.ts
@@ -7,6 +7,7 @@ import {
   authConfig,
 } from '@shared/config';
 import { UsersModule } from '@users/interface-adapters';
+import { AuthModule } from '@auth/interface-adapters';
 
 import { AppController } from './app.controller';
 import { AppService } from './app.service';
@@ -18,6 +19,7 @@ import { AppService } from './app.service';
       load: [userAppConfig, databaseConfig, awsConfig, authConfig],
     }),
     UsersModule,
+    AuthModule,
   ],
   controllers: [AppController],
   providers: [AppService],
diff --git a/libs/auth/application/src/lib/auth.service.ts b/libs/auth/application/src/lib/auth.service.ts
index 9412771..7a0fd14 100644
--- a/libs/auth/application/src/lib/auth.service.ts
+++ b/libs/auth/application/src/lib/auth.service.ts
@@ -1,15 +1,16 @@
-import { Logger, UnauthorizedException } from '@nestjs/common';
+import { Injectable, Logger, UnauthorizedException } from '@nestjs/common';
 import { UsersService } from '@users/application';
 import { JwtService } from '@nestjs/jwt';
 import { AwsCognitoService } from '@shared/infrastructure-aws-cognito';
 
 // Implement the authentication logic
+@Injectable()
 export class AuthService {
+  private readonly logger = new Logger(AuthService.name);
   constructor(
     private awsCognitoService: AwsCognitoService,
     private usersService: UsersService,
     private jwtService: JwtService,
-    private readonly logger = new Logger(AuthService.name),
   ) {}
 
   // Retrieving a user and verifying the password
diff --git a/libs/auth/interface-adapters/src/lib/auth.module.ts b/libs/auth/interface-adapters/src/lib/auth.module.ts
index f1d7b84..29ee385 100644
--- a/libs/auth/interface-adapters/src/lib/auth.module.ts
+++ b/libs/auth/interface-adapters/src/lib/auth.module.ts
@@ -1,27 +1,54 @@
 import { AuthService } from '@auth/application';
 import { Module } from '@nestjs/common';
-import { ConfigService } from '@nestjs/config';
-import { JwtModule } from '@nestjs/jwt';
+import { ConfigModule, ConfigService } from '@nestjs/config';
+import { MongooseModule } from '@nestjs/mongoose';
+import { JwtModule, JwtService } from '@nestjs/jwt';
+import { AwsCognitoService } from '@shared/infrastructure-aws-cognito';
+import { DatabaseModule } from '@shared/infrastructure-mongoose';
+import { GetUserUseCase, UsersService } from '@users/application';
+import { USERS_REPOSITORY } from '@users/domain';
+import {
+  MongooseUsersRepository,
+  UserDocument,
+  UserSchema,
+} from '@users/infrastructure-mongoose';
 import { UsersModule } from '@users/interface-adapters';
 
 import { AuthResolver } from './resolver/auth.resolver';
 
 @Module({
+  providers: [
+    AuthResolver,
+    AuthService,
+    AwsCognitoService,
+    UsersService,
+    JwtService,
+    GetUserUseCase,
+    {
+      provide: USERS_REPOSITORY,
+      useClass: MongooseUsersRepository,
+    },
+  ],
   imports: [
     UsersModule,
     JwtModule.registerAsync({
       global: true,
+      imports: [ConfigModule],
+      inject: [ConfigService],
       useFactory: (configService: ConfigService) => {
-        const jwtConfig = configService.get('jwt');
+        const authConfig = configService.get('auth');
+
         return {
-          secret: jwtConfig.secret,
+          secret: authConfig.secret,
           signOptions: { expiresIn: '60s' },
         };
       },
-      inject: [ConfigService],
     }),
+    DatabaseModule,
+    MongooseModule.forFeature([
+      { name: UserDocument.name, schema: UserSchema },
+    ]),
   ],
-  providers: [AuthResolver, AuthService],
   exports: [AuthService],
 })
 export class AuthModule {}
diff --git a/libs/auth/interface-adapters/src/lib/dto/sign-in-input.dto.ts b/libs/auth/interface-adapters/src/lib/dto/sign-in-input.dto.ts
index 34293f1..58f4ede 100644
--- a/libs/auth/interface-adapters/src/lib/dto/sign-in-input.dto.ts
+++ b/libs/auth/interface-adapters/src/lib/dto/sign-in-input.dto.ts
@@ -1,5 +1,6 @@
-import { Field } from '@nestjs/graphql';
+import { Field, InputType } from '@nestjs/graphql';
 
+@InputType()
 export class SignInInputDto {
   @Field()
   email!: string;
diff --git a/libs/auth/interface-adapters/src/lib/resolver/auth.resolver.ts b/libs/auth/interface-adapters/src/lib/resolver/auth.resolver.ts
index 39dad6e..2b58926 100644
--- a/libs/auth/interface-adapters/src/lib/resolver/auth.resolver.ts
+++ b/libs/auth/interface-adapters/src/lib/resolver/auth.resolver.ts
@@ -1,20 +1,24 @@
 import { AuthService } from '@auth/application';
-import { Resolver, Mutation, Args } from '@nestjs/graphql';
+import { Resolver, Mutation, Args, Field, ObjectType } from '@nestjs/graphql';
 
 import { SignInInputDto } from '../dto/sign-in-input.dto';
 
+@ObjectType()
+export class Response {
+  @Field()
+  accessToken!: string;
+}
+
 // Expose the authentication endpoints
 @Resolver()
 export class AuthResolver {
   constructor(private authService: AuthService) {}
 
-  @Mutation()
+  @Mutation(() => Response)
   async signIn(
     @Args({ name: 'signInInput', type: () => SignInInputDto })
     signInInput: SignInInputDto,
-  ): Promise<{
-    accessToken: string;
-  }> {
+  ): Promise<Response> {
     return this.authService.signIn(signInInput.email, signInInput.password);
   }
 }
diff --git a/libs/users/interface-adapters/src/lib/dto/user.dto.ts b/libs/users/interface-adapters/src/lib/dto/user.dto.ts
index fd61646..108d6c7 100644
--- a/libs/users/interface-adapters/src/lib/dto/user.dto.ts
+++ b/libs/users/interface-adapters/src/lib/dto/user.dto.ts
@@ -1,4 +1,4 @@
-import { IsEmail, IsString } from 'class-validator';
+import { IsEmail, IsOptional } from 'class-validator';
 import { Field, ID, ObjectType } from '@nestjs/graphql';
 
 @ObjectType()
@@ -10,12 +10,12 @@ export class UserDto {
   @IsEmail()
   email: string;
 
-  @Field()
-  @IsString()
-  firstName?: string | null;
+  @Field(() => String, { nullable: true })
+  @IsOptional()
+  firstName: string | null;
 
-  @Field()
-  @IsString()
+  @Field(() => String, { nullable: true })
+  @IsOptional()
   lastName: string | null;
 
   constructor(