How to use worker threads?

0-2 years experience

1. 1We need to offload a CPU‑intensive image resize operation. How would you set up a Worker thread in Node.js to handle a single image file?
2. 2If you spawn a Worker and forget to call worker.terminate(), what will happen when the main process exits?

2-5 years experience

1. 1Your new feature processes user‑uploaded CSV files in parallel using Worker threads, but you notice occasional 'ERR_WORKER_NOT_RUNNING' errors. Walk me through how you'd debug this.
2. 2When deciding between a Worker thread pool and spawning a new Worker per request, what trade‑offs would you consider for a service handling 200 requests per second?
3. 3Explain how you would pass large JSON data to a Worker without copying it unnecessarily.

5-8 years experience

1. 1Our microservice uses Worker threads for heavy calculations, but under load memory usage spikes. How would you redesign the threading model to keep memory bounded?
2. 2Design a strategy to gracefully shut down a Node.js server that has multiple active Workers processing jobs, ensuring no data loss.
3. 3What are the implications of using SharedArrayBuffer vs message passing for coordinating state between Workers in a high‑throughput system?

8+ years experience

1. 1We plan to migrate a legacy monolith that currently uses child_process for parallel work to Worker threads across several teams. What architectural considerations and migration steps would you propose?
2. 2How would you evaluate whether introducing Worker threads at the platform level is worth the operational complexity compared to moving compute‑heavy parts to a separate service written in another language?
3. 3Discuss the long‑term maintenance challenges of a codebase that heavily relies on Worker threads for concurrency, especially regarding debugging, monitoring, and onboarding new engineers.