I had a Node.js video-processing API throwing 503s every time someone uploaded a 4K clip. The default fix everyone reaches for — cluster.fork() across cores — actually made it worse. Throughput dropped 40%. The right answer…
| Error | What it means / fix |
|---|---|
| UnhandledPromise | Express.js async error handling that actually works in 2026 Express.js async error handling that actually works in 2026: Express 5 native catching, the express-async-errors patch for legacy apps, typed error classes, and the Sentry integration that survives a bad deploy. |
| MODULE_NOT_FOUND | Fix “Cannot find module” in Node.js (CommonJS, ES modules, TypeScript) Fix Cannot find module in Node.js: CommonJS vs ESM resolution rules, TypeScript path aliases at runtime, file case-sensitivity, monorepo workspace pitfalls, and the diagnostic tree I hand new engineers. |
| EADDRINUSE | Fix EADDRINUSE: address already in use in Node.js (Mac, Linux, Windows) Fix EADDRINUSE: address already in use in Node.js on Mac, Linux, and Windows. The kill commands per OS, the TIME_WAIT trap, graceful shutdown, and how to stop it from coming back. |
I rebuilt the same Node.js API five times last month — once on each of the major frameworks — to settle a question a client kept asking: "what should we use in 2026?" Same workload (a customer-orders REST…
