Express Server Performance Tips for Production

Express Server Performance Tips for Production

Express is fine out of the box, but production needs more. Here are real performance tips.

1. Use Cluster or PM2

A single Node process uses one CPU core. Use the cluster module or PM2 to spawn one worker per CPU. This scales across cores.

2. Add Compression

Add compression middleware to gzip JSON responses. Cuts payload size and improves perceived performance.

3. Cache Where You Can

Cache expensive queries in Redis. Cache hot API responses with a short TTL. Cache HTTP responses with Cache-Control headers where appropriate.

4. Use Connection Pooling for MongoDB

Mongoose uses pooling. Set poolSize to match expected concurrency (default 100 is usually fine). Avoid one connection per request.

5. Keep Handlers Async

Never block the event loop with sync work. Read files with fs.promises, hash with bcrypt (async), call DB with await. Skip fs.readFileSync in request handlers.

6. Use Lean Queries

If you only need to send JSON, use .lean() on Mongoose queries. Skips hydrating full documents, which is faster.

7. Add Indexes in MongoDB

Index the fields you query and sort by. Without indexes, MongoDB scans the whole collection. Use explain() to verify queries use indexes.

8. Buffer and Stream Large Responses

For large data, stream instead of buffering the whole thing. For file uploads, stream to a destination instead of holding in memory.

9. Limit Payload Size

Set a limit on JSON body parsing: express.json({ limit: '10kb' }). This prevents oversized payload attacks.

10. Use HTTP/2 With Nginx

Behind Nginx, enable HTTP/2. Express itself uses HTTP/1.1, but Nginx in front can use HTTP/2 with the client. Multiplexing improves latency.

11. Use a Process Manager

PM2 keeps the server alive, restarts on crash, and lets you reload without downtime. Run the server under PM2 in production.

12. Monitor Event Loop Lag

Use tools like clinic.js or the built-in --inspect to measure event loop lag. If lag grows, something is blocking. Find and fix it.

The Takeaway

Express production performance: use cluster or PM2, add compression, cache with Redis, use DB connection pooling, keep handlers async, use lean queries, add indexes, stream large responses, limit payload size, use HTTP/2 with Nginx, use a process manager, and monitor event loop lag.