Response Compression with gzip and Brotli

Large API responses transfer unnecessary bytes. Clients that accept compression get no benefit because the server sends uncompressed responses by default.

Enable response compression middleware to automatically compress eligible responses.

import compression from 'compression';

app.use(compression({
  // Only compress responses larger than 1KB
  threshold: 1024,
  // Custom filter — skip streaming responses
  filter: (req, res) => {
    if (req.headers['x-no-compression']) return false;
    return compression.filter(req, res);
  },
  level: 6, // Balance between speed and compression ratio
}));

// Verify compression is working:
// curl -H 'Accept-Encoding: gzip' -I https://api.example.com/users
// Should see: Content-Encoding: gzip

// For static files served by nginx, prefer nginx-level compression
// over Node.js — nginx is significantly more efficient

HTTP compression reduces JSON response size by 60-80%. The Content-Encoding header tells clients how to decode the response. The Accept-Encoding header tells the server what algorithms the client supports.