NODE.JS GUIDE
Node.js Worker Threads Interview Guide
By the HireReadyAI team · 8 min read
When to offload CPU work, how messaging works, and how workers differ from child processes.
When to use workers
Use worker threads for CPU-heavy JavaScript: image transforms, crypto at scale, large JSON transforms, compression. Do not use them for ordinary I/O — async I/O already overlaps well on the main thread.
Programming model
Workers receive messages and can share memory via SharedArrayBuffer in advanced cases. Most apps post messages with structured data and return results. Pool workers if you create many tasks; spinning a thread per request can be costly.
Workers vs child processes
Child processes isolate memory more strongly and can run non-JS binaries. Workers are lighter for parallel JS. Both keep the event loop responsive if you move CPU work off the main thread.
Interview answer
“Node’s main thread should stay free for I/O callbacks. For CPU-bound work I offload to worker threads or another service, measure event-loop delay, and avoid blocking JSON.parse on huge payloads in request handlers.”