agent-skills/skills/nestjs-best-practices/rules/security-rate-limiting.md

---
title: Implement Rate Limiting
impact: HIGH
impactDescription: Protects against abuse and ensures fair resource usage
tags: security, rate-limiting, throttler, protection
---

## Implement Rate Limiting

Use `@nestjs/throttler` to limit request rates per client. Apply different limits for different endpoints - stricter for auth endpoints, more relaxed for read operations. Consider using Redis for distributed rate limiting in clustered deployments.

**Incorrect (no rate limiting on sensitive endpoints):**

```typescript
// No rate limiting on sensitive endpoints
@Controller('auth')
export class AuthController {
  @Post('login')
  async login(@Body() dto: LoginDto): Promise<TokenResponse> {
    // Attackers can brute-force credentials
    return this.authService.login(dto);
  }

  @Post('forgot-password')
  async forgotPassword(@Body() dto: ForgotPasswordDto): Promise<void> {
    // Can be abused to spam users with emails
    return this.authService.sendResetEmail(dto.email);
  }
}

// Same limits for all endpoints
@UseGuards(ThrottlerGuard)
@Controller('api')
export class ApiController {
  @Get('public-data')
  async getPublic() {} // Should allow more requests

  @Post('process-payment')
  async payment() {} // Should be more restrictive
}
```

**Correct (configured throttler with endpoint-specific limits):**

```typescript
// Configure throttler globally with multiple limits
import { ThrottlerModule, ThrottlerGuard } from '@nestjs/throttler';

@Module({
  imports: [
    ThrottlerModule.forRoot([
      {
        name: 'short',
        ttl: 1000, // 1 second
        limit: 3, // 3 requests per second
      },
      {
        name: 'medium',
        ttl: 10000, // 10 seconds
        limit: 20, // 20 requests per 10 seconds
      },
      {
        name: 'long',
        ttl: 60000, // 1 minute
        limit: 100, // 100 requests per minute
      },
    ]),
  ],
  providers: [
    {
      provide: APP_GUARD,
      useClass: ThrottlerGuard,
    },
  ],
})
export class AppModule {}

// Override limits per endpoint
@Controller('auth')
export class AuthController {
  @Post('login')
  @Throttle({ short: { limit: 5, ttl: 60000 } }) // 5 attempts per minute
  async login(@Body() dto: LoginDto): Promise<TokenResponse> {
    return this.authService.login(dto);
  }

  @Post('forgot-password')
  @Throttle({ short: { limit: 3, ttl: 3600000 } }) // 3 per hour
  async forgotPassword(@Body() dto: ForgotPasswordDto): Promise<void> {
    return this.authService.sendResetEmail(dto.email);
  }
}

// Skip throttling for certain routes
@Controller('health')
export class HealthController {
  @Get()
  @SkipThrottle()
  check(): string {
    return 'OK';
  }
}

// Custom throttle per user type
@Injectable()
export class CustomThrottlerGuard extends ThrottlerGuard {
  protected async getTracker(req: Request): Promise<string> {
    // Use user ID if authenticated, IP otherwise
    return req.user?.id || req.ip;
  }

  protected async getLimit(context: ExecutionContext): Promise<number> {
    const request = context.switchToHttp().getRequest();

    // Higher limits for authenticated users
    if (request.user) {
      return request.user.isPremium ? 1000 : 200;
    }

    return 50; // Anonymous users
  }
}
```

Reference: [NestJS Throttler](https://docs.nestjs.com/security/rate-limiting)