nodejs-development

Avoid synchronous I/O in request handlers and offload CPU-intensive work over 50ms to worker threads. Use async/await for all I/O, prefer setImmediate over setTimeout(fn, 0), and monitor event loop lag with clinic.js or --prof.

Use worker threads for CPU-bound tasks like hashing, compression, or large JSON parsing. Use streams for I/O-bound work like processing large files or proxying data, where backpressure and memory efficiency matter.

Use ESM for new projects by setting "type": "module" in package.json. ESM supports top-level await and better tree-shaking. Never mix require() and import in the same file; migrate existing CommonJS projects incrementally.

Distinguish operational errors (validation, timeouts) from programmer errors (bugs). Always catch async errors since unhandled rejections crash Node 16+, use custom error classes, log with context, and crash on programmer errors with a restart.

Common causes include unbounded global caches, event listener leaks, and closure leaks in handlers. Use LRU caches, track and remove listeners, monitor with process.memoryUsage(), and tune --max-old-space-size.

Listen for SIGTERM and SIGINT, stop accepting new requests with server.close(), finish in-flight requests with a timeout, close database connections, flush logs, then exit. This prevents dropped requests during deployments.