diff --git a/apps/api/src/app/BUILD.bazel b/apps/api/src/app/BUILD.bazel
index dcea6df..f6805a6 100644
--- a/apps/api/src/app/BUILD.bazel
+++ b/apps/api/src/app/BUILD.bazel
@@ -13,7 +13,7 @@ ts_library(
         "//apps/api/src/auth",
         "//apps/api/src/cats",
         "//apps/api/src/user",
-        "//libs/api-interface/src",
+        "//libs/proto-interface/src",
         "@npm//@nestjs/common",
         "@npm//@nestjs/passport",
         "@npm//@nestjs/swagger",
diff --git a/apps/api/src/app/app.controller.ts b/apps/api/src/app/app.controller.ts
index d66af2d..b2b2918 100644
--- a/apps/api/src/app/app.controller.ts
+++ b/apps/api/src/app/app.controller.ts
@@ -2,7 +2,7 @@ import { Controller, Get, UseGuards } from '@nestjs/common';
 import { AuthGuard } from '@nestjs/passport';
 import { ApiBearerAuth } from '@nestjs/swagger';
 
-import { Message } from '@api-interface';
+import { IMessage } from '@proto-interface';
 
 import { AppService } from './app.service';
 
@@ -13,7 +13,7 @@ export class AppController {
 
   @Get('hello')
   @UseGuards(AuthGuard('jwt'))
-  getData(): Message {
+  getData(): Required<IMessage> {
     return this.appService.getData();
   }
 }
diff --git a/apps/api/src/app/app.service.ts b/apps/api/src/app/app.service.ts
index cf43fac..d232d10 100644
--- a/apps/api/src/app/app.service.ts
+++ b/apps/api/src/app/app.service.ts
@@ -1,9 +1,9 @@
-import { Message } from '@api-interface';
 import { Injectable } from '@nestjs/common';
+import { IMessage } from '@proto-interface';
 
 @Injectable()
 export class AppService {
-  getData(): Message {
+  getData(): Required<IMessage> {
     return { message: 'Welcome to api!' };
   }
 }
diff --git a/apps/api/src/auth/BUILD.bazel b/apps/api/src/auth/BUILD.bazel
index 15e46ac..bd15ecb 100644
--- a/apps/api/src/auth/BUILD.bazel
+++ b/apps/api/src/auth/BUILD.bazel
@@ -11,7 +11,7 @@ ts_library(
     module_name = "@api/auth",
     deps = [
         "//apps/api/src/user",
-        "//libs/api-interface/src",
+        "//libs/proto-interface/src",
         "@npm//@nestjs/common",
         "@npm//@nestjs/jwt",
         "@npm//@nestjs/passport",
diff --git a/apps/api/src/auth/auth.service.ts b/apps/api/src/auth/auth.service.ts
index 2d2f203..33ad862 100644
--- a/apps/api/src/auth/auth.service.ts
+++ b/apps/api/src/auth/auth.service.ts
@@ -1,6 +1,6 @@
-import { SignedUser } from '@api-interface';
 import { Injectable } from '@nestjs/common';
 import { JwtService } from '@nestjs/jwt';
+import { ISignedUser } from '@proto-interface';
 import { UserService } from '../user/user.service';
 import { JwtPayload } from './interfaces/jwt-payload.interface';
 
@@ -13,7 +13,7 @@ export class AuthService {
     private readonly jwtService: JwtService,
   ) {}
 
-  async createToken(username: string): Promise<SignedUser> {
+  async createToken(username: string): Promise<Required<ISignedUser>> {
     const { firstName, lastName } = await this.userService.getUserByUsername(username);
     const payload: JwtPayload = { username, firstName, lastName };
 
diff --git a/apps/api/src/cats/BUILD.bazel b/apps/api/src/cats/BUILD.bazel
index be76229..7c357d1 100644
--- a/apps/api/src/cats/BUILD.bazel
+++ b/apps/api/src/cats/BUILD.bazel
@@ -10,7 +10,7 @@ ts_library(
     ),
     module_name = "@api/cats",
     deps = [
-        "//libs/api-interface/src",
+        "//libs/proto-interface/src",
         "@npm//@nestjs/common",
         "@npm//@nestjs/passport",
         "@npm//@nestjs/swagger",
diff --git a/apps/api/src/cats/dto/create-cat.dto.ts b/apps/api/src/cats/dto/create-cat.dto.ts
index 69f8ed7..d67b9e1 100644
--- a/apps/api/src/cats/dto/create-cat.dto.ts
+++ b/apps/api/src/cats/dto/create-cat.dto.ts
@@ -1,8 +1,8 @@
-import { ICreateCatDto } from '@api-interface';
 import { ApiModelProperty } from '@nestjs/swagger';
+import { ICreateCatDto } from '@proto-interface';
 import { IsInt, IsNotEmpty, Max, Min } from 'class-validator';
 
-export class CreateCatDto implements ICreateCatDto {
+export class CreateCatDto implements Required<ICreateCatDto> {
   @ApiModelProperty()
   @IsNotEmpty()
   name: string;
diff --git a/apps/api/src/cats/entities/cat.ts b/apps/api/src/cats/entities/cat.ts
index 89f03d1..bffaad7 100644
--- a/apps/api/src/cats/entities/cat.ts
+++ b/apps/api/src/cats/entities/cat.ts
@@ -1,8 +1,8 @@
-import { CatModel } from '@api-interface';
+import { ICat } from '@proto-interface';
 import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';
 
 @Entity()
-export class Cat implements CatModel {
+export class Cat implements Required<ICat> {
   @PrimaryGeneratedColumn()
   id: number;
 
diff --git a/apps/api/src/user/BUILD.bazel b/apps/api/src/user/BUILD.bazel
index 8763d2d..7ebb1a1 100644
--- a/apps/api/src/user/BUILD.bazel
+++ b/apps/api/src/user/BUILD.bazel
@@ -10,7 +10,7 @@ ts_library(
     ),
     module_name = "@api/user",
     deps = [
-        "//libs/api-interface/src",
+        "//libs/proto-interface/src",
         "@npm//@nestjs/common",
         "@npm//@nestjs/passport",
         "@npm//@nestjs/swagger",
diff --git a/apps/api/src/user/dto/sign-in.dto.ts b/apps/api/src/user/dto/sign-in.dto.ts
index e2d01e8..5d74417 100644
--- a/apps/api/src/user/dto/sign-in.dto.ts
+++ b/apps/api/src/user/dto/sign-in.dto.ts
@@ -1,8 +1,8 @@
-import { ISignInDto } from '@api-interface';
 import { ApiModelProperty } from '@nestjs/swagger';
+import { ISignInDto } from '@proto-interface';
 import { IsNotEmpty, IsString } from 'class-validator';
 
-export class SignInDto implements ISignInDto {
+export class SignInDto implements Required<ISignInDto> {
   @ApiModelProperty()
   @IsString()
   @IsNotEmpty()
diff --git a/apps/api/src/user/dto/sign-up.dto.ts b/apps/api/src/user/dto/sign-up.dto.ts
index 3d8d51d..661b151 100644
--- a/apps/api/src/user/dto/sign-up.dto.ts
+++ b/apps/api/src/user/dto/sign-up.dto.ts
@@ -1,8 +1,8 @@
-import { ISignUpDto } from '@api-interface';
 import { ApiModelProperty } from '@nestjs/swagger';
+import { ISignUpDto } from '@proto-interface';
 import { IsNotEmpty, IsString } from 'class-validator';
 
-export class SignUpDto implements ISignUpDto {
+export class SignUpDto implements Required<ISignUpDto> {
   @ApiModelProperty()
   @IsString()
   @IsNotEmpty()
diff --git a/apps/api/src/user/entities/user.entity.ts b/apps/api/src/user/entities/user.entity.ts
index 18c88fb..21a6c8c 100644
--- a/apps/api/src/user/entities/user.entity.ts
+++ b/apps/api/src/user/entities/user.entity.ts
@@ -1,8 +1,8 @@
-import { UserModel } from '@api-interface';
+import { IUser } from '@proto-interface';
 import { Column, Entity, PrimaryGeneratedColumn } from 'typeorm';
 
 @Entity()
-export class User implements UserModel {
+export class User implements Required<IUser> {
   @PrimaryGeneratedColumn()
   id: number;
 
diff --git a/apps/lazy-loading-app/src/app/app.component.ts b/apps/lazy-loading-app/src/app/app.component.ts
index e209dce..2574f44 100644
--- a/apps/lazy-loading-app/src/app/app.component.ts
+++ b/apps/lazy-loading-app/src/app/app.component.ts
@@ -1,12 +1,12 @@
 import { Component } from '@angular/core';
 import { Router } from '@angular/router';
-import { SignedUser } from '@api-interface';
+import { ISignedUser } from '@proto-interface';
 
 import { AuthenticationService } from './auth/authentication.service';
 
 @Component({ selector: 'lazy-root', templateUrl: 'app.component.html' })
 export class AppComponent {
-  currentUser: SignedUser;
+  currentUser: Required<ISignedUser>;
 
   constructor(
     private router: Router,
diff --git a/apps/lazy-loading-app/src/app/auth/BUILD.bazel b/apps/lazy-loading-app/src/app/auth/BUILD.bazel
index 336e173..f7e2aa0 100644
--- a/apps/lazy-loading-app/src/app/auth/BUILD.bazel
+++ b/apps/lazy-loading-app/src/app/auth/BUILD.bazel
@@ -10,7 +10,7 @@ ng_module(
     ),
     tsconfig = "//:tsconfig.json",
     deps = [
-        "//libs/api-interface/src",
+        "//libs/proto-interface/src",
         "@npm//@angular/common",
         "@npm//@angular/core",
         "@npm//@angular/router",
diff --git a/apps/lazy-loading-app/src/app/auth/authentication.service.ts b/apps/lazy-loading-app/src/app/auth/authentication.service.ts
index ed685e5..f1a06b1 100644
--- a/apps/lazy-loading-app/src/app/auth/authentication.service.ts
+++ b/apps/lazy-loading-app/src/app/auth/authentication.service.ts
@@ -1,26 +1,28 @@
 import { HttpClient } from '@angular/common/http';
 import { Injectable } from '@angular/core';
-import { ISignUpDto, SignedUser } from '@api-interface';
+import { ISignedUser, ISignUpDto } from '@proto-interface';
 import { BehaviorSubject, Observable } from 'rxjs';
 import { map } from 'rxjs/operators';
 
 @Injectable()
 export class AuthenticationService {
-    private currentUserSubject: BehaviorSubject<SignedUser>;
-    public currentUser: Observable<SignedUser>;
+    private currentUserSubject: BehaviorSubject<Required<ISignedUser>>;
+    public currentUser: Observable<Required<ISignedUser>>;
     private apiUrl = 'http://localhost:3000';
 
     constructor(private http: HttpClient) {
-        this.currentUserSubject = new BehaviorSubject<SignedUser>(JSON.parse(localStorage.getItem('currentUser')));
+        this.currentUserSubject = new BehaviorSubject<Required<ISignedUser>>(
+          JSON.parse(localStorage.getItem('currentUser')),
+        );
         this.currentUser = this.currentUserSubject.asObservable();
     }
 
-    public get currentUserValue(): SignedUser {
+    public get currentUserValue(): Required<ISignedUser> {
         return this.currentUserSubject.value;
     }
 
     login(username: string, password: string) {
-        return this.http.post<SignedUser>(`${this.apiUrl}/auth/sign-in`, { username, password })
+        return this.http.post<Required<ISignedUser>>(`${this.apiUrl}/auth/sign-in`, { username, password })
             .pipe(map((user) => {
                 // login successful if there's a jwt token in the response
                 if (user && user.token) {
@@ -33,7 +35,7 @@ export class AuthenticationService {
             }));
     }
 
-    register(user: ISignUpDto) {
+    register(user: Required<ISignUpDto>) {
       return this.http.post(`${this.apiUrl}/auth/sign-up`, user);
     }
 
diff --git a/apps/lazy-loading-app/src/app/home/BUILD.bazel b/apps/lazy-loading-app/src/app/home/BUILD.bazel
index d9a51cb..36bdb70 100644
--- a/apps/lazy-loading-app/src/app/home/BUILD.bazel
+++ b/apps/lazy-loading-app/src/app/home/BUILD.bazel
@@ -13,7 +13,7 @@ ng_module(
     deps = [
         "//apps/lazy-loading-app/src/app/alert",
         "//apps/lazy-loading-app/src/app/auth",
-        "//libs/api-interface/src",
+        "//libs/proto-interface/src",
         "@npm//@angular/common",
         "@npm//@angular/core",
         "@npm//@angular/forms",
diff --git a/apps/lazy-loading-app/src/app/home/cats.service.ts b/apps/lazy-loading-app/src/app/home/cats.service.ts
index f1b41f2..bb34622 100644
--- a/apps/lazy-loading-app/src/app/home/cats.service.ts
+++ b/apps/lazy-loading-app/src/app/home/cats.service.ts
@@ -1,6 +1,6 @@
 import { HttpClient } from '@angular/common/http';
 import { Injectable } from '@angular/core';
-import { CatModel, ICreateCatDto } from '@api-interface';
+import { ICat, ICreateCatDto } from '@proto-interface';
 import { Observable } from 'rxjs';
 
 @Injectable()
@@ -9,19 +9,19 @@ export class CatsService {
 
   constructor(private http: HttpClient) {}
 
-  getAll(): Observable<CatModel[]> {
-    return this.http.get<CatModel[]>(`${this.apiUrl}/cats`);
+  getAll(): Observable<Array<Required<ICat>>> {
+    return this.http.get<Array<Required<ICat>>>(`${this.apiUrl}/cats`);
   }
 
-  getById(id: number): Observable<CatModel> {
-    return this.http.get<CatModel>(`${this.apiUrl}/cats/${id}`);
+  getById(id: number): Observable<Required<ICat>> {
+    return this.http.get<Required<ICat>>(`${this.apiUrl}/cats/${id}`);
   }
 
-  create(createCatDto: ICreateCatDto): Observable<CatModel> {
-    return this.http.post<CatModel>(`${this.apiUrl}/cats`, createCatDto);
+  create(createCatDto: Required<ICreateCatDto>): Observable<Required<ICat>> {
+    return this.http.post<Required<ICat>>(`${this.apiUrl}/cats`, createCatDto);
   }
 
-  delete(id: number): Observable<CatModel> {
-    return this.http.delete<CatModel>(`${this.apiUrl}/cats/${id}`);
+  delete(id: number): Observable<Required<ICat>> {
+    return this.http.delete<Required<ICat>>(`${this.apiUrl}/cats/${id}`);
   }
 }
diff --git a/apps/lazy-loading-app/src/app/home/home.component.ts b/apps/lazy-loading-app/src/app/home/home.component.ts
index 4582fc1..7992412 100644
--- a/apps/lazy-loading-app/src/app/home/home.component.ts
+++ b/apps/lazy-loading-app/src/app/home/home.component.ts
@@ -1,6 +1,6 @@
 import { Component, OnDestroy, OnInit } from '@angular/core';
 import { AbstractControl, FormBuilder, FormGroup, Validators } from '@angular/forms';
-import { CatModel, ICreateCatDto, SignedUser } from '@api-interface';
+import { ICat, ICreateCatDto, ISignedUser } from '@proto-interface';
 import { Subscription } from 'rxjs';
 import { first } from 'rxjs/operators';
 
@@ -10,9 +10,9 @@ import { CatsService } from './cats.service';
 
 @Component({ templateUrl: 'home.component.html' })
 export class HomeComponent implements OnInit, OnDestroy {
-  currentUser: SignedUser;
+  currentUser: Required<ISignedUser>;
   currentUserSubscription: Subscription;
-  cats: CatModel[] = [];
+  cats: Array<Required<ICat>> = [];
 
   catForm: FormGroup;
   loading = false;
@@ -53,7 +53,7 @@ export class HomeComponent implements OnInit, OnDestroy {
     }
 
     this.loading = true;
-    const createCatDto: ICreateCatDto = {
+    const createCatDto: Required<ICreateCatDto> = {
       name: this.f.name.value,
       age: this.f.age.value,
     };
diff --git a/libs/proto-interface/README.md b/libs/proto-interface/README.md
new file mode 100644
index 0000000..671402d
--- /dev/null
+++ b/libs/proto-interface/README.md
@@ -0,0 +1,25 @@
+# ApiInterface
+
+This library was generated with [Angular CLI](https://github.com/angular/angular-cli) version 7.2.0.
+
+## Code scaffolding
+
+Run `ng generate component component-name --project api-interface` to generate a new component. You can also use `ng generate directive|pipe|service|class|guard|interface|enum|module --project api-interface`.
+
+> Note: Don't forget to add `--project api-interface` or else it will be added to the default project in your `angular.json` file.
+
+## Build
+
+Run `ng build api-interface` to build the project. The build artifacts will be stored in the `dist/` directory.
+
+## Publishing
+
+After building your library with `ng build api-interface`, go to the dist folder `cd dist/api-interface` and run `npm publish`.
+
+## Running unit tests
+
+Run `ng test api-interface` to execute the unit tests via [Karma](https://karma-runner.github.io).
+
+## Further help
+
+To get more help on the Angular CLI use `ng help` or go check out the [Angular CLI README](https://github.com/angular/angular-cli/blob/master/README.md).
diff --git a/libs/proto-interface/jest.config.js b/libs/proto-interface/jest.config.js
new file mode 100644
index 0000000..14d5b08
--- /dev/null
+++ b/libs/proto-interface/jest.config.js
@@ -0,0 +1,5 @@
+module.exports = {
+  name: "api-interface",
+  preset: "../../jest.config.js",
+  coverageDirectory: "../../coverage/libs/api-interface"
+};
diff --git a/libs/proto-interface/src/BUILD.bazel b/libs/proto-interface/src/BUILD.bazel
new file mode 100644
index 0000000..a55afeb
--- /dev/null
+++ b/libs/proto-interface/src/BUILD.bazel
@@ -0,0 +1,21 @@
+package(default_visibility = ["//:__subpackages__"])
+
+load("@npm_bazel_typescript//:index.bzl", "ts_library", "ts_proto_library")
+
+proto_library(
+    name = "proto",
+    srcs = glob(["*.proto"]),
+)
+
+ts_proto_library(
+    name = "ts_proto",
+    deps = [":proto"],
+)
+
+ts_library(
+    name = "src",
+    srcs = glob(["index.ts"]),
+    module_name = "@proto-interface",
+    tsconfig = "//:tsconfig.json",
+    deps = [":ts_proto"],
+)
diff --git a/libs/proto-interface/src/cat.proto b/libs/proto-interface/src/cat.proto
new file mode 100644
index 0000000..5a00c4e
--- /dev/null
+++ b/libs/proto-interface/src/cat.proto
@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+message Cat {
+  int32 id = 1;
+  string name = 2;
+  int32 age = 3;
+}
+
+message CreateCatDto {
+  string name = 1;
+  int32 age = 2;
+}
diff --git a/libs/proto-interface/src/index.ts b/libs/proto-interface/src/index.ts
new file mode 100644
index 0000000..3a9f70c
--- /dev/null
+++ b/libs/proto-interface/src/index.ts
@@ -0,0 +1,10 @@
+export {
+  ICat,
+  ICreateCatDto,
+  IMessage,
+  IUser,
+  ISignUpDto,
+  ISignInDto,
+  ISignedUser,
+// @ts-ignore
+} from './ts_proto';
diff --git a/libs/proto-interface/src/message.proto b/libs/proto-interface/src/message.proto
new file mode 100644
index 0000000..0694981
--- /dev/null
+++ b/libs/proto-interface/src/message.proto
@@ -0,0 +1,5 @@
+syntax = "proto3";
+
+message Message {
+  string message = 1;
+}
diff --git a/libs/proto-interface/src/user.proto b/libs/proto-interface/src/user.proto
new file mode 100644
index 0000000..4900e1f
--- /dev/null
+++ b/libs/proto-interface/src/user.proto
@@ -0,0 +1,29 @@
+syntax = "proto3";
+
+message User {
+  int32 id = 1;
+  string username = 2;
+  string firstName = 3;
+  string lastName = 4;
+  string password = 5;
+}
+
+message SignUpDto {
+  string username = 1;
+  string firstName = 2;
+  string lastName = 3;
+  string password = 4;
+}
+
+message SignInDto {
+  string username = 1;
+  string password = 2;
+}
+
+message SignedUser {
+  string username = 1;
+  string firstName = 2;
+  string lastName = 3;
+  int32 expiresIn = 4;
+  string token = 5;
+}
diff --git a/libs/proto-interface/tsconfig.json b/libs/proto-interface/tsconfig.json
new file mode 100644
index 0000000..e5decd5
--- /dev/null
+++ b/libs/proto-interface/tsconfig.json
@@ -0,0 +1,7 @@
+{
+  "extends": "../../tsconfig.json",
+  "compilerOptions": {
+    "types": ["node", "jest"]
+  },
+  "include": ["**/*.ts"]
+}
diff --git a/libs/proto-interface/tsconfig.lib.json b/libs/proto-interface/tsconfig.lib.json
new file mode 100644
index 0000000..6a7446f
--- /dev/null
+++ b/libs/proto-interface/tsconfig.lib.json
@@ -0,0 +1,18 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc/libs/api-interface",
+    "target": "es2015",
+    "module": "es2015",
+    "moduleResolution": "node",
+    "declaration": true,
+    "sourceMap": true,
+    "inlineSources": true,
+    "emitDecoratorMetadata": true,
+    "experimentalDecorators": true,
+    "importHelpers": true,
+    "types": [],
+    "lib": ["dom", "es2018"]
+  },
+  "exclude": ["src/test.ts", "**/*.spec.ts"]
+}
diff --git a/libs/proto-interface/tsconfig.spec.json b/libs/proto-interface/tsconfig.spec.json
new file mode 100644
index 0000000..5040bbc
--- /dev/null
+++ b/libs/proto-interface/tsconfig.spec.json
@@ -0,0 +1,9 @@
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "outDir": "../../dist/out-tsc/libs/api-interface",
+    "module": "commonjs",
+    "types": ["jest", "node"]
+  },
+  "include": ["**/*.spec.ts", "**/*.d.ts"]
+}
diff --git a/libs/proto-interface/tslint.json b/libs/proto-interface/tslint.json
new file mode 100644
index 0000000..4fa9be3
--- /dev/null
+++ b/libs/proto-interface/tslint.json
@@ -0,0 +1,4 @@
+{
+  "extends": "../../tslint.json",
+  "rules": []
+}
diff --git a/tsconfig.json b/tsconfig.json
index d2c0657..90403bb 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -13,16 +13,8 @@
     "typeRoots": [
       "node_modules/@types"
     ],
-//    "lib": [
-//      "dom",
-//      "es5",
-//      "es2015.collection",
-//      "es2015.iterable",
-//      "es2015.promise"
-//    ],
     "rootDirs": [
-      "./apps/lazy-loading-app/src",
-      "./dist/bin/apps/lazy-loading-app/src"
+      "./dist/bin"
     ],
     "lib": [
       "es2017",
@@ -35,6 +27,9 @@
     "paths": {
       "@api-interface": [
         "libs/api-interface/src/index.ts"
+      ],
+      "@proto-interface": [
+        "dist/bin/libs/proto-interface/src/index"
       ]
     }
   },