Title: Beyond the Hype: How Node.js Actually Handles Concurrency (Event Loop + libuv)
Post (Markdown):
Node.js is often described as “single‑threaded”, but that’s only true for JavaScript execution. The real concurrency story is asynchronous I/O + native code.
1) The Event Loop is an orchestrator
When you start an I/O task (filesystem, networking, DNS), Node.js delegates the heavy lifting to the operating system and/or libuv. Meanwhile, the JS thread stays free to keep the app responsive.
2) Why native (C/C++) matters
JavaScript can’t directly access low‑level OS primitives. Node relies on native bindings to bridge:
JS → C/C++ (libuv, V8 internals) → OS → back to JS
3) The thread pool is for “can’t block the loop” work
Some tasks are too expensive to run on the JS thread (CPU‑heavy or certain blocking operations). Node offloads these into libuv’s thread pool (configurable via UV_THREADPOOL_SIZE) to avoid freezing the event loop.
Key takeaway:
Single JS thread ≠ low performance. It means one thread for JS, plus native concurrency under the hood.
Hashtags: #nodejs #backend #javascript #performance #systems
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