How do you use environment variables in Node.js?

Short answer: You can access environment variables using process.env. const port = process.env.PORT || 3000; These variables are set outside your app, often in your shell or deployment environment.

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.