nestjs_rest_api_best_practices.md

Building efficient, reliable, and secure REST APIs involves following several best practices. Here's a detailed breakdown of these practices, including versioning, security, and optimization techniques for your NestJS-based microservice:

1. API Design & Structure

• Resource Naming: Use meaningful, clear, and consistent names for your endpoints (e.g., /movies, /movies/{id}). Prefer nouns for resources and use HTTP methods to represent actions (GET, POST, PUT, DELETE).
• HTTP Methods:
  • GET for reading data.
  • POST for creating resources.
  • PUT or PATCH for updating resources.
  • DELETE for removing resources.
• Use HTTP Status Codes: Return appropriate status codes (e.g., 200 for success, 201 for created, 404 for not found, 400 for bad request, 500 for server errors).

2. API Versioning

Versioning is crucial for maintaining backward compatibility. There are several ways to handle versioning:

• URL-based versioning (most common):
  Example: GET /api/v1/movies
• Header-based versioning:
  Example: GET /movies with a header Accept: application/vnd.company.v1+json
• Query Parameter-based versioning:
  Example: GET /movies?version=1

In NestJS, you can easily version your API using @nestjs/versioning:

import { VersioningType } from '@nestjs/common';

app.enableVersioning({
  type: VersioningType.URI,
});

3. Security Best Practices

• Authentication:
  • Use JWT (JSON Web Tokens) for stateless authentication. Use libraries like @nestjs/jwt for easy integration.
  • Optionally, OAuth2 for third-party integrations.
• Authorization:
  • Use role-based or permission-based access control.
  • Implement guards in NestJS using @nestjs/passport and custom decorators to manage roles.
• Data Validation & Sanitization:
  • Use class-validator and class-transformer to validate and sanitize incoming requests, ensuring only valid data is processed.

  @IsString()
  @IsNotEmpty()
  title: string;

• Use HTTPS: Ensure secure communication by enforcing HTTPS.
• CORS: Configure CORS settings to restrict unauthorized domains from accessing your API.

  app.enableCors({
    origin: ['https://trustedwebsite.com'], // Allow specific domains
  });

• Rate Limiting: Protect your API from brute-force attacks by limiting the number of requests a user can make. Use NestJS's @nestjs/throttler package for rate limiting.

  import { ThrottlerModule } from '@nestjs/throttler';
  
  @Module({
    imports: [ThrottlerModule.forRoot({
      ttl: 60,
      limit: 10, // Limit 10 requests per minute per IP
    })],
  })
  export class AppModule {}

4. Error Handling

• Use global exception filters in NestJS to ensure consistent error responses across your API.
• Ensure errors are descriptive and standardized. Respond with meaningful messages and status codes.
• Example:

  throw new HttpException('Movie not found', HttpStatus.NOT_FOUND);

5. Logging & Monitoring

• Structured Logging: Use a logger like winston or NestJS's built-in logging functionality. Log essential events, errors, and critical API activity.
• Monitoring: Use tools like Prometheus or New Relic to monitor API performance and uptime. Consider exposing a health-check endpoint (/health) to monitor service status.
• Error Tracking: Integrate tools like Sentry to track and manage errors.

6. Performance Optimization

• Pagination: When fetching large datasets (like movies), implement pagination, filtering, and sorting to improve performance. Example: GET /movies?page=1&limit=10&sort=title.
• Database Optimization:
  • Use indexes for frequently queried fields.
  • Use lazy loading for related entities when necessary.
• Caching: Use Redis or in-memory caching for frequently requested data to reduce database load.
• Rate Limiting & Throttling: Control the number of requests a client can make to prevent API overuse.

7. Testing

• Unit Testing: Ensure each function is tested with NestJS's built-in @nestjs/testing module.
• Integration Testing: Write integration tests to ensure that all components of the API work together properly.
• End-to-End Testing: Use tools like Supertest or Postman to simulate requests and check API behavior.

8. Documentation

• API Documentation: Use Swagger to automatically generate API documentation for your endpoints.

  import { SwaggerModule, DocumentBuilder } from '@nestjs/swagger';
  
  const config = new DocumentBuilder()
    .setTitle('Movies API')
    .setDescription('The movies API documentation')
    .setVersion('1.0')
    .build();
  const document = SwaggerModule.createDocument(app, config);
  SwaggerModule.setup('api', app, document);

9. Database Management

• Migrations: Use migration tools (like TypeORM's migration system or Sequelize's migration feature) to manage database changes and schema versions.
• Data Validation: Implement validation at the database level (unique constraints, foreign keys, etc.) to ensure data integrity.

10. CI/CD & Deployment

• Automate your testing, build, and deployment pipelines using CI/CD tools (GitHub Actions, Jenkins, CircleCI).
• Implement environment-specific configurations using .env files and ensure sensitive data (e.g., API keys) is encrypted or stored in secure vaults.

11. API Deprecation Strategy

• Graceful Deprecation: When deprecating old API versions, provide warnings or notices to users well in advance.
• Versioning for Deprecation: Continue to support older versions while encouraging users to migrate to the newer version.

Would you like to focus on any particular section first, such as security, versioning, or performance? Let me know how you'd like to proceed!