Real-world Use Cases?

Short answer: 🏦 Fintech API – Global Exception Filter Ensures consistent error envelopes across microservices. 🛠 Microservices – Audit Logging Tracks when sensitive controller actions are executed. 👮 Role-based Authorization Custom authorization filter validating role claims dynamically. 🚀 Performance Profiling Times how long each controller method takes. public class ProfilingFilter : IActionFilter

Example code

{
private Stopwatch _watch;
public void OnActionExecuting(ActionExecutingContext context)
{
_watch = Stopwatch.StartNew();
}
public void OnActionExecuted(ActionExecutedContext context)
{ _watch.Stop(); Console.WriteLine($"Action took {_watch.ElapsedMilliseconds} ms"); }
}

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.