How do you monitor performance in a Node.js app?

Short answer: Use monitoring tools like New Relic, Datadog, AppDynamics, or open-source tools like Prometheus + Grafana. Track metrics: response time, CPU/memory usage, error rates. Use Node.js built-in profilers or clinic.js to analyze performance. Set up alerts for anomalies.

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.