What is the difference between CommonJS and ES Modules (ESM) in Node.js?

Short answer: CommonJS (CJS): Uses require() and module.exports. Synchronous module loading. ES Modules: Uses import/export syntax. Supports asynchronous and static analysis. ESM is the modern standard but Node.js supports both.

Real-world example (ShopNest)

A ShopNest BFF in Node.js aggregates catalog and price APIs for the React storefront.

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.