What is the difference between synchronous and asynchronous functions?

Short answer: Synchronous functions block the execution until they finish. Asynchronous functions allow other code to run while waiting for operations (like I/O) to complete. // Synchronous (blocks event loop) const data = fs.readFileSync('file.txt'); // Asynchronous (non-blocking) fs.readFile('file.txt', (err, data) => { if (err) throw err; console.log(data); });

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.