Scalability: load balancing, statelessness?

Short answer: Design apps to be stateless so any server instance can handle requests. Use distributed caches or external session stores. Load balancers distribute traffic to multiple instances.

Real-world example (ShopNest)

A ShopNest checkout request flows through middleware, hits a minimal API or controller, uses scoped services, and returns ProblemDetails on errors.

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.