juniorNode.js
Junior Question 1: What is Node.js and why is it single-threaded?
Updated May 4, 2026
Short answer
Node.js is a JavaScript runtime built on Chrome's V8 engine. It uses a single-threaded event loop for non-blocking I/O.
Deep explanation
While the JavaScript execution is single-threaded, Node uses libuv to handle system tasks in the background using a thread pool. This allows Node to handle thousands of concurrent connections without the overhead of thread context switching.
Real-world example
Building a real-time chat app where many users connect simultaneously.
Common mistakes
- Thinking Node is completely single-threaded (it isn't
- libuv uses a thread pool for disk/crypto).
Follow-up questions
- What is libuv?