Why does CPU-bound work on the main thread hurt Node.js performance?
Because Node.js is single-threaded. While CPU-bound work runs, no other request can be processed. This is the biggest performance mistake in Node.js. Offload CPU-heavy work to worker threads.
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More FAQs in CPU-Bound vs I/O-Bound Work in Node.js: How to Handle Each
I/O-bound work (database, file, network) waits for external systems, and Node.js handles it with non-blocking I/O via the event loop. CPU-bound work (computation) uses the CPU and blocks the main thread, requiring worker threads to offload.
Use async APIs: fs.readFile, fetch, database queries with promises. The event loop stays free while I/O completes. Use Promise.all for multiple independent operations to parallelize them.
Offload to worker threads. CPU-heavy work on the main thread blocks all requests. Worker threads run the computation on a separate thread, keeping the event loop free. Use worker_threads for image processing, crypto, and large data work.
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