Worker Threads in Node.js: When and How to Use Them

Worker Threads in Node.js: When and How to Use Them Your API hashes a password. The event loop blocks. Every other request waits. Node is single-threaded, but it does not have to be. The Problem CPU-bound work (hashing, image processing, JSON parsing large payloads, compression) blocks the event loop. While Node processes that work, it cannot handle incoming requests, timers, or I/O callbacks. Basic Worker Thread import { Worker , isMainThread , parentPort , workerData } from " worker_threads " ; if ( isMainThread ) { const worker = new Worker ( __filename , { workerData : { input : " heavy-task " } }); worker . on ( " message " , ( result ) => console . log ( " Result: " , result )); worker . on ( " error " , ( err ) => console . error ( " Worker error: " , err )); } else { // This runs in a separate thread const result = heavyComputation ( workerData . input ); parentPort ?. postMessage ( result ); } Worker Pool Creating a new worker per request is expensive. Pool them: import { Work