Explain the difference between callbacks, promises, and async/await.

Short answer: Callbacks: Functions passed as arguments, executed when async operation finishes. Can lead to “callback hell.” Promises: Objects representing future results; allow chaining with .then(). Async/await: Syntactic sugar over promises; lets you write async code that looks synchronous, improving readability.

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.