Explain the non-blocking I/O model in Node.js.

Short answer: Non-blocking I/O means the application doesn't wait for a task (like reading a file or querying a database) to complete before moving to the next one. Node.js uses callbacks, promises, or async/await to handle the results when they're ready. 📌

Example code

const fs = require('fs'); fs.readFile('file.txt', 'utf8', (err, data) => { if (err) throw err; console.log(data); }); console.log('Reading file...'); You’ll see "Reading file..." first, even though the file is being read.

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.