Optimizing the performance of an Express.js application is crucial for delivering a fast and responsive user experience. Here are the top 10 best practices to ensure your Express.js application renders quickly:

1. Enable Gzip Compression

Compressing response bodies can significantly reduce the amount of data sent over the network. Use compression middleware to enable gzip compression.

const compression = require('compression');
const express = require('express');
const app = express();

app.use(compression());

2. Use Caching

Implementing caching strategies can dramatically reduce the time spent on data retrieval. Consider in-memory caching (like node-cache) or caching HTTP responses with express-redis-cache.

const cache = require('node-cache');
const myCache = new cache();

app.get('/data', (req, res) => {
  let data = myCache.get('key');
  if (!data) {
    // Fetch data from database
    data = fetchDataFromDatabase();
    myCache.set('key', data, 10000); // Cache for 10 seconds
  }
  res.send(data);
});

3. Optimize Middleware Usage

Use only the necessary middleware and avoid unnecessary processing. Ensure middleware is specific to the routes that need them.

app.use('/api', apiRouter); // Only apply API router middleware to /api routes

4. Leverage Asynchronous Operations

Avoid blocking the event loop. Use asynchronous operations with async/await to handle I/O operations efficiently.

app.get('/data', async (req, res) => {
  try {
    const data = await fetchDataFromDatabase();
    res.send(data);
  } catch (error) {
    res.status(500).send(error);
  }
});

5. Use a Reverse Proxy

Deploy your application behind a reverse proxy server like Nginx or HAProxy. This setup can handle load balancing, SSL termination, and caching, offloading these tasks from your Node.js server.

# Example Nginx configuration snippet
server {
    listen 80;
    server_name example.com;

    location / {
        proxy_pass http://localhost:3000;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
    }
}

6. Implement Route-Level Caching

Cache the output of specific routes where data does not change frequently.

const apicache = require('apicache');
const cache = apicache.middleware;

app.get('/api/some-endpoint', cache('5 minutes'), (req, res) => {
  // Data processing logic
});

7. Minimize Static File Serving

Serve static files efficiently using a CDN or optimize them using tools like Webpack to bundle and minify. Use express.static only for minimal files.

app.use(express.static('public', { maxAge: '1d' })); // Cache static files for 1 day

8. Optimize Database Queries

Ensure database queries are optimized and avoid N+1 query problems. Use indexes and proper query optimization techniques.

app.get('/users', async (req, res) => {
  try {
    const users = await User.find().lean(); // .lean() returns plain JS objects instead of Mongoose documents
    res.send(users);
  } catch (error) {
    res.status(500).send(error);
  }
});

9. Use Clustering

Utilize all CPU cores by clustering your Node.js process. The cluster module can spawn multiple worker processes, making better use of multi-core systems.

const cluster = require('cluster');
const numCPUs = require('os').cpus().length;

if (cluster.isMaster) {
  // Fork workers.
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }
} else {
  // Workers can share any TCP connection
  // In this case, it is an HTTP server
  require('./server.js');
}

10. Monitor and Profile Performance

Regularly monitor your application using tools like pm2, New Relic, or node-inspector. Profiling helps identify bottlenecks and optimize critical paths.

// Using PM2 for monitoring
// Start your app with PM2
pm2 start app.js --name "my-express-app"

// Monitor with PM2
pm2 monit

Conclusion

Applying these best practices can significantly enhance the performance of your Express.js applications, leading to faster response times and better user experiences. Prioritize and implement optimizations based on your application’s specific needs and workload.

Ollayor's Blog

Top 10 Best Practices in Express.js