Node.js Performance Tips

Performance matters. Here are the techniques I use to keep Node.js applications fast and responsive.

1. Understand the Event Loop

The event loop is the heart of Node.js. Blocking it means slow responses for everyone.

// ❌ Bad: Blocking operation
function processData(data) {
  const result = heavyComputation(data); // Blocks event loop
  return result;
}

// ✅ Good: Non-blocking with setImmediate
function processData(data, callback) {
  setImmediate(() => {
    const result = heavyComputation(data);
    callback(result);
  });
}

2. Use Caching Strategically

import NodeCache from 'node-cache';

const cache = new NodeCache({ stdTTL: 300 }); // 5 min TTL

async function getUser(id) {
  const cached = cache.get(`user:${id}`);
  if (cached) return cached;
  
  const user = await db.users.findById(id);
  cache.set(`user:${id}`, user);
  return user;
}

3. Database Optimization

• Use connection pooling
• Add proper indexes
• Paginate large queries
• Use projections to fetch only needed fields

// ❌ Fetching everything
const users = await User.find({});

// ✅ Paginated with projection
const users = await User.find({})
  .select('name email avatar')
  .skip(page * limit)
  .limit(limit)
  .lean();

4. Use Streams for Large Data

import { createReadStream } from 'fs';
import { pipeline } from 'stream/promises';

// Stream large files instead of loading into memory
app.get('/download/:file', async (req, res) => {
  const stream = createReadStream(`./files/${req.params.file}`);
  await pipeline(stream, res);
});

Key Takeaways

1. Never block the event loop
2. Cache aggressively but invalidate wisely
3. Optimize database queries
4. Use streams for large data
5. Monitor and profile regularly

Happy optimizing!