SMRTR ProgrammingJul 23, 2026Daily.dev

Stop Calling Node.js “Single-Threaded”: A Look Under the Hood

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Node.js isn't truly single-threaded — it offloads slow I/O operations to Libuv, a C library that interfaces with the OS, keeping the main JS thread free. The event loop then processes callbacks in strict priority order: synchronous code first, then all microtasks (Promises), then one macrotask (setTimeout) at a time, repeating until queues are empty.

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