What is event loop blocking, and how do you detect it?

Short answer: Blocking happens when synchronous code takes too long, preventing other events from processing. Detect with tools like: clinic.js — Event Loop Delay tool. Manual timing (setInterval to check delay).

Real-world example (ShopNest)

ShopNest’s Node API handles many checkout requests concurrently because I/O (DB/HTTP) is non-blocking on the event loop.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.