When would you use worker threads in Node.js?
For heavy CPU computation like image processing, crypto on the JS side, or large data processing. Worker threads run your code on separate threads, keeping the main thread's event loop free for other requests.
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More FAQs in Thread Pool and Worker Threads Interview Questions for Node.js
A pool of 4 threads (default) in libuv that handles operations the OS cannot do asynchronously: certain fs operations, dns.lookup, and some crypto. These run off the main thread, and callbacks run on the main thread via the event loop.
File system operations (fs module), DNS lookups (dns.lookup), some crypto operations (crypto.pbkdf2, crypto.scrypt), and some zlib operations. Network I/O does not; it uses the OS's async capabilities directly.
The thread pool is internal to libuv and handles specific I/O operations automatically. Worker threads are a Node.js API where your JavaScript code runs on separate threads for CPU-heavy computation. The thread pool is for I/O; worker threads are for computation.
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