NestJS, a framework for building efficient, scalable Node.js applications, provides a solid foundation for backend development. However, as applications grow, performance can become a concern. Fortunately, there are several strategies to improve performance in your NestJS applications. This blog will navigate through some of these key techniques.

1. Use Caching Wisely

Caching is one of the most effective ways to boost application performance by reducing the number of times data is fetched from the database or an external API.

Example

You can use the built-in CacheModule in NestJS:

import { Module, CacheModule } from '@nestjs/common';

@Module({
  imports: [
    CacheModule.register({
      ttl: 5, // seconds
      max: 100, // maximum number of items in cache
    }),
    // other modules
  ],
})
export class AppModule {}

In your service, you could use decorators like @CacheKey() and @CacheTTL() to specify how long specific data should be cached.

import { Injectable, Cacheable } from '@nestjs/common';

@Injectable()
export class UsersService {
  @Cacheable()
  async findAll() {
    // fetch users from the database
  }
}

2. Optimize Database Queries

Database queries can often be a bottleneck. Optimizing your queries and reducing the number of calls to the database can significantly improve performance.

Example

Using TypeORM with NestJS, you might want to choose specific fields you need instead of fetching the entire object.

// Fetch only specific fields
const users = await this.userRepository.find({
  select: ['id', 'name', 'email'], // only return these fields
});

Additionally, consider using query builders to write efficient queries tailored to your data needs.

const users = await this.userRepository.createQueryBuilder('user')
  .where('user.active = :active', { active: true })
  .getMany();

3. Use Asynchronous Patterns Effectively

NestJS is built on top of asynchronous programming with Promises and Observables. Make sure to leverage async/await and RxJS operators for non-blocking calls.

Example

When dealing with multiple asynchronous requests, using Promise.all() can help speed up the process:

async getUserData(ids: number[]) {
  const userPromises = ids.map(id => this.usersService.findOne(id));
  return await Promise.all(userPromises); // resolves all promises concurrently
}

4. Limit Middleware and Use Guards Wisely

While middleware serves a specific purpose, it can sometimes lead to performance bottlenecks, especially if they perform heavy operations.

Example

Avoid using too many middleware functions on routes unless necessary. Use guards to handle authorization and validation efficiently.

@UseGuards(JwtAuthGuard)
@Get('profile')
async getProfile(@Request() req) {
  return this.usersService.findOne(req.user.id);
}

5. Compress HTTP Responses

Reducing the size of HTTP responses can reduce load time and enhance response time. Using compression middleware is a simple way to implement this.

Example

Install the compression package:

npm install compression

Add the middleware to your main.ts file:

import * as compression from 'compression';
import { NestFactory } from '@nestjs/core';
import { AppModule } from './app.module';

async function bootstrap() {
  const app = await NestFactory.create(AppModule);
  app.use(compression());
  await app.listen(3000);
}
bootstrap();

6. Enable Gzip and Brotli Compression

Not only can you use compression middleware, but you can also enable gzip or Brotli compression to reduce the payload size further.

Example

To implement Brotli exchange, you can utilize the express-static-gzip middleware:

npm install express-static-gzip

In your main.ts, include it like so:

import express from 'express';
import expressStaticGzip from 'express-static-gzip';

app.use('/static', expressStaticGzip('public', {
  enableBrotli: true,
  orderPreference: ['br', 'gz']
}));

7. Monitor Performance Metrics

Finally, it’s essential to monitor your app's performance regularly. Utilizing tools like Prometheus, Grafana, or NewRelic can help identify slow endpoints and resource-heavy processes.

Example

You can integrate Prometheus by using prom-client:

npm install prom-client

Track metrics like response time or request count, allowing you to visualize your application’s behavior over time.

import { collectDefaultMetrics, Registry } from 'prom-client';

// Setup Prometheus
const register = new Registry();
collectDefaultMetrics({ register });

// Add your custom metrics here

By incorporating these strategies, you can effectively enhance the performance of your NestJS applications, ensuring they scale efficiently and respond swiftly to users' requests. Continue to explore these possibilities and adapt your approach according to specific application needs, harnessing the full potential of NestJS for modern backend development.