diff --git a/apps/users-application/src/users/users.resolver.spec.ts b/apps/users-application/src/users/users.resolver.spec.ts
index e962238..26fcae9 100644
--- a/apps/users-application/src/users/users.resolver.spec.ts
+++ b/apps/users-application/src/users/users.resolver.spec.ts
@@ -1,7 +1,7 @@
 import { Test, TestingModule } from '@nestjs/testing';
 import { UsersResolver } from './users.resolver';
 import { UsersService } from './users.service';
-import { User } from './models/user.model';
+import { User } from '@user/domain';
 
 describe('UsersResolver', () => {
   let resolver: UsersResolver;
@@ -30,35 +30,35 @@ describe('UsersResolver', () => {
 
   describe('getUser', () => {
     it('should return a user by id', () => {
-      const user: User = { id: 1, name: 'John Doe' };
+      const user: User = { id: '1', name: 'John Doe' };
       jest.spyOn(service, 'findById').mockReturnValue(user);
 
-      expect(resolver.getUser(1)).toEqual(user);
-      expect(service.findById).toHaveBeenCalledWith(1);
+      expect(resolver.getUser('1')).toEqual(user);
+      expect(service.findById).toHaveBeenCalledWith('1');
     });
 
     it('should return undefined if user not found', () => {
       jest.spyOn(service, 'findById').mockReturnValue(undefined);
 
-      expect(resolver.getUser(1)).toBeUndefined();
-      expect(service.findById).toHaveBeenCalledWith(1);
+      expect(resolver.getUser('2')).toBeUndefined();
+      expect(service.findById).toHaveBeenCalledWith('2');
     });
   });
 
   describe('resolveReference', () => {
     it('should return a user by reference id', () => {
-      const user: User = { id: 1, name: 'John Doe' };
+      const user: User = { id: '1', name: 'John Doe' };
       jest.spyOn(service, 'findById').mockReturnValue(user);
 
-      expect(resolver.resolveReference({ __typename: 'User', id: 1 })).toEqual(user);
-      expect(service.findById).toHaveBeenCalledWith(1);
+      expect(resolver.resolveReference({ __typename: 'User', id: '1' })).toEqual(user);
+      expect(service.findById).toHaveBeenCalledWith('1');
     });
 
     it('should return undefined if user not found by reference id', () => {
       jest.spyOn(service, 'findById').mockReturnValue(undefined);
 
-      expect(resolver.resolveReference({ __typename: 'User', id: 1 })).toBeUndefined();
-      expect(service.findById).toHaveBeenCalledWith(1);
+      expect(resolver.resolveReference({ __typename: 'User', id: '2' })).toBeUndefined();
+      expect(service.findById).toHaveBeenCalledWith('2');
     });
   });
 });
\ No newline at end of file
diff --git a/apps/users-application/src/users/users.resolver.ts b/apps/users-application/src/users/users.resolver.ts
index 27c438d..be678b7 100644
--- a/apps/users-application/src/users/users.resolver.ts
+++ b/apps/users-application/src/users/users.resolver.ts
@@ -1,6 +1,6 @@
 import { Args, ID, Query, Resolver, ResolveReference } from '@nestjs/graphql';
+import { User } from '@user/domain';
 
-import { User } from './models/user.model';
 import { UsersService } from './users.service';
 
 @Resolver(() => User)
@@ -8,14 +8,14 @@ export class UsersResolver {
   constructor(private usersService: UsersService) {}
 
   @Query(() => User, { nullable: true })
-  getUser(@Args({ name: 'id', type: () => ID }) id: number): User | undefined {
+  getUser(@Args({ name: 'id', type: () => ID }) id: string): User | undefined {
     return this.usersService.findById(id);
   }
 
   @ResolveReference()
   resolveReference(reference: {
     __typename: string;
-    id: number;
+    id: string;
   }): User | undefined {
     return this.usersService.findById(reference.id);
   }
diff --git a/apps/users-application/src/users/users.service.spec.ts b/apps/users-application/src/users/users.service.spec.ts
index a253487..17af965 100644
--- a/apps/users-application/src/users/users.service.spec.ts
+++ b/apps/users-application/src/users/users.service.spec.ts
@@ -1,6 +1,7 @@
 import { Test, TestingModule } from '@nestjs/testing';
+import { User } from '@user/domain';
+
 import { UsersService } from './users.service';
-import { User } from './models/user.model';
 
 describe('UsersService', () => {
   let service: UsersService;
@@ -18,12 +19,12 @@ describe('UsersService', () => {
   });
 
   it('should return a user by id', () => {
-    const user: User = service.findById(1);
-    expect(user).toEqual({ id: 1, name: 'John Doe' });
+    const user: User = service.findById('1');
+    expect(user).toEqual({ id: '1', name: 'John Doe' });
   });
 
   it('should return undefined if user is not found', () => {
-    const user: User = service.findById(3);
+    const user: User = service.findById('3');
     expect(user).toBeUndefined();
   });
 });
\ No newline at end of file
diff --git a/apps/users-application/src/users/users.service.ts b/apps/users-application/src/users/users.service.ts
index 6048d31..e9757b0 100644
--- a/apps/users-application/src/users/users.service.ts
+++ b/apps/users-application/src/users/users.service.ts
@@ -1,14 +1,14 @@
 import { Injectable } from '@nestjs/common';
-import { User } from './models/user.model';
+import { User } from '@user/domain';
 
 @Injectable()
 export class UsersService {
   private users: User[] = [
-    { id: 1, name: 'John Doe' },
-    { id: 2, name: 'Richard Roe' },
+    { id: '1', name: 'John Doe' },
+    { id: '2', name: 'Richard Roe' },
   ];
 
-  findById(id: number): User | undefined {
-    return this.users.find((user) => user.id === Number(id));
+  findById(id: string): User | undefined {
+    return this.users.find((user) => user.id === id);
   }
-}
\ No newline at end of file
+}
diff --git a/libs/user/domain/README.md b/libs/user/domain/README.md
new file mode 100644
index 0000000..b3a89ab
--- /dev/null
+++ b/libs/user/domain/README.md
@@ -0,0 +1,7 @@
+# domain
+
+This library was generated with [Nx](https://nx.dev).
+
+## Running unit tests
+
+Run `nx test domain` to execute the unit tests via [Jest](https://jestjs.io).
diff --git a/libs/user/domain/eslint.config.js b/libs/user/domain/eslint.config.js
new file mode 100644
index 0000000..07e518f
--- /dev/null
+++ b/libs/user/domain/eslint.config.js
@@ -0,0 +1,3 @@
+const baseConfig = require('../../../eslint.config.js');
+
+module.exports = [...baseConfig];
diff --git a/libs/user/domain/jest.config.ts b/libs/user/domain/jest.config.ts
new file mode 100644
index 0000000..4334d1b
--- /dev/null
+++ b/libs/user/domain/jest.config.ts
@@ -0,0 +1,10 @@
+export default {
+  displayName: 'domain',
+  preset: '../../../jest.preset.js',
+  testEnvironment: 'node',
+  transform: {
+    '^.+\\.[tj]s$': ['ts-jest', { tsconfig: '<rootDir>/tsconfig.spec.json' }],
+  },
+  moduleFileExtensions: ['ts', 'js', 'html'],
+  coverageDirectory: '../../../coverage/libs/user/domain',
+};
diff --git a/libs/user/domain/project.json b/libs/user/domain/project.json
new file mode 100644
index 0000000..e7be118
--- /dev/null
+++ b/libs/user/domain/project.json
@@ -0,0 +1,9 @@
+{
+  "name": "domain",
+  "$schema": "../../../node_modules/nx/schemas/project-schema.json",
+  "sourceRoot": "libs/user/domain/src",
+  "projectType": "library",
+  "tags": [],
+  "// targets": "to see all targets run: nx show project domain --web",
+  "targets": {}
+}
diff --git a/libs/user/domain/src/index.ts b/libs/user/domain/src/index.ts
new file mode 100644
index 0000000..2dbc61e
--- /dev/null
+++ b/libs/user/domain/src/index.ts
@@ -0,0 +1 @@
+export * from './lib/user.entity';
diff --git a/libs/user/domain/src/lib/user.entity.spec.ts b/libs/user/domain/src/lib/user.entity.spec.ts
new file mode 100644
index 0000000..7e91f5c
--- /dev/null
+++ b/libs/user/domain/src/lib/user.entity.spec.ts
@@ -0,0 +1,15 @@
+import { User } from './user.entity';
+
+describe('User Entity', () => {
+  it('should create a user with id and name', () => {
+    const user = new User('1', 'John Doe');
+    expect(user.id).toBe('1');
+    expect(user.name).toBe('John Doe');
+  });
+
+  it('should allow updating the name', () => {
+    const user = new User('1', 'John Doe');
+    user.name = 'Jane Doe';
+    expect(user.name).toBe('Jane Doe');
+  });
+});
\ No newline at end of file
diff --git a/libs/user/domain/src/lib/user.entity.ts b/libs/user/domain/src/lib/user.entity.ts
new file mode 100644
index 0000000..202554e
--- /dev/null
+++ b/libs/user/domain/src/lib/user.entity.ts
@@ -0,0 +1,6 @@
+export class User {
+  constructor(
+    public readonly id: string,
+    public name: string,
+  ) {}
+}
diff --git a/libs/user/domain/tsconfig.json b/libs/user/domain/tsconfig.json
new file mode 100644
index 0000000..0dc79ca
--- /dev/null
+++ b/libs/user/domain/tsconfig.json
@@ -0,0 +1,22 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "module": "commonjs",
+    "forceConsistentCasingInFileNames": true,
+    "strict": true,
+    "noImplicitOverride": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "noPropertyAccessFromIndexSignature": true
+  },
+  "files": [],
+  "include": [],
+  "references": [
+    {
+      "path": "./tsconfig.lib.json"
+    },
+    {
+      "path": "./tsconfig.spec.json"
+    }
+  ]
+}
diff --git a/libs/user/domain/tsconfig.lib.json b/libs/user/domain/tsconfig.lib.json
new file mode 100644
index 0000000..e583571
--- /dev/null
+++ b/libs/user/domain/tsconfig.lib.json
@@ -0,0 +1,11 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "module": "commonjs",
+    "outDir": "../../../dist/out-tsc",
+    "declaration": true,
+    "types": ["node"]
+  },
+  "exclude": ["jest.config.ts", "src/**/*.spec.ts", "src/**/*.test.ts"],
+  "include": ["src/**/*.ts"]
+}
diff --git a/libs/user/domain/tsconfig.spec.json b/libs/user/domain/tsconfig.spec.json
new file mode 100644
index 0000000..69a251f
--- /dev/null
+++ b/libs/user/domain/tsconfig.spec.json
@@ -0,0 +1,14 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../../dist/out-tsc",
+    "module": "commonjs",
+    "types": ["jest", "node"]
+  },
+  "include": [
+    "jest.config.ts",
+    "src/**/*.test.ts",
+    "src/**/*.spec.ts",
+    "src/**/*.d.ts"
+  ]
+}
diff --git a/tsconfig.base.json b/tsconfig.base.json
index 91bb2ed..58a3b4a 100644
--- a/tsconfig.base.json
+++ b/tsconfig.base.json
@@ -15,15 +15,14 @@
     "skipDefaultLibCheck": true,
     "baseUrl": ".",
     "paths": {
-      "@libs/config": [
-        "libs/config/src/index.ts"
-      ],
+      "@libs/config": ["libs/config/src/index.ts"],
       "@prompt/user-prompt-log-entity": [
         "libs/prompt/domain/user-prompt-log-entity/src/index.ts"
       ],
       "@prompt/wellbeing-prompt-entity": [
         "libs/prompt/domain/wellbeing-prompt-entity/src/index.ts"
-      ]
+      ],
+      "@user/domain": ["libs/user/domain/src/index.ts"]
     }
   },
   "exclude": ["node_modules", "tmp"]