Creating RESTful APIs with NestJS for Scalable Backends

Creating RESTful APIs with NestJS for Scalable Backends

Modern web applications rely heavily on RESTful APIs to connect the frontend with the backend. As these applications scale, their APIs need to be reliable, modular, and easy to maintain. NestJS, a progressive Node.js framework built with TypeScript, provides the structure and flexibility needed to develop robust APIs efficiently.

NestJS is inspired by Angular’s architecture and embraces the use of decorators, dependency injection, and a modular system , making it an ideal choice for teams familiar with TypeScript and looking to build large-scale server-side applications.

This guide walks through the core concepts of NestJS and demonstrates how to build a simple but scalable RESTful API.

Why Choose NestJS?

NestJS stands out in the Node.js ecosystem for several reasons:

• TypeScript-first: Strong typing and IDE support
• Modular architecture: Organize code by feature and responsibility
• Dependency injection: Promotes testability and clean design
• Built-in support for routing, middleware, pipes, guards, and more
• Ecosystem integrations: With tools like TypeORM, Prisma, Swagger, and GraphQL

It strikes a balance between opinionated structure and flexible design, making it suitable for both startups and enterprise applications.

Getting Started

1. Install the NestJS CLI

npm install -g @nestjs/cli
nest new my-api

The CLI scaffolds a ready-to-run project with TypeScript, a main.ts bootstrap file, and a default AppModule.

2. Create a Module, Controller, and Service

NestJS encourages splitting logic into:

• Modules: Grouping of related features
• Controllers: Handling HTTP routes
• Services: Business logic and data access

Let’s build a basic Users module.

nest generate module users
nest generate controller users
nest generate service users

This creates structured files under src/users for controller, service, and module configuration.

3. Define a User Entity (DTO)

In users/dto/create-user.dto.ts:

export class CreateUserDto {
  readonly name: string;
  readonly email: string;
}

You can later add validation decorators like @IsEmail() using the class-validator package.

4. Implement the Users Controller

In users.controller.ts:

import { Controller, Get, Post, Body, Param } from '@nestjs/common';
import { UsersService } from './users.service';
import { CreateUserDto } from './dto/create-user.dto';

@Controller('users')
export class UsersController {
  constructor(private readonly usersService: UsersService) {}

  @Get()
  findAll() {
    return this.usersService.findAll();
  }

  @Get(':id')
  findOne(@Param('id') id: string) {
    return this.usersService.findOne(+id);
  }

  @Post()
  create(@Body() createUserDto: CreateUserDto) {
    return this.usersService.create(createUserDto);
  }
}

5. Add Business Logic in the Service

In users.service.ts:

import { Injectable } from '@nestjs/common';
import { CreateUserDto } from './dto/create-user.dto';

@Injectable()
export class UsersService {
  private users = [];

  findAll() {
    return this.users;
  }

  findOne(id: number) {
    return this.users.find(user => user.id === id);
  }

  create(dto: CreateUserDto) {
    const newUser = { id: Date.now(), ...dto };
    this.users.push(newUser);
    return newUser;
  }
}

For now, users are stored in memory , in a real app, you’d connect to a database using an ORM like TypeORM or Prisma.

Enhancing Your API

Once you’ve set up the basics, consider adding:

• Validation: Use @nestjs/class-validator for input validation
• Swagger Documentation: Add @nestjs/swagger for auto-generated API docs
• Authentication: Use guards and strategies with Passport.js
• Error handling: Use custom filters for consistent error responses
• Database integration: Add PostgreSQL, MongoDB, or MySQL support
• Testing: Built-in tools for unit and integration testing

The modular nature of NestJS makes it easy to plug in features as your application grows.

Conclusion

NestJS provides a robust, TypeScript-powered framework for building RESTful APIs with clarity and scale in mind. With its strong architecture and ecosystem support, you can focus on writing business logic without worrying about the underlying boilerplate.

Whether you’re building a microservice, a full-stack application backend, or a public API, NestJS gives you the tools to create well-structured, production-ready code from day one.

Disclaimer

Article written with the help of AI.

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