Custom authorization policies and handlers Define complex authorization rules using IAuthorizationHandler: public class MinimumAgeRequirement : IAuthorizationRequirement { public int Age { get; } public MinimumAgeRequirement(int age) => Age = age; } public class MinimumAgeHandler :

Short answer: uthorizationHandler<MinimumAgeRequirement> { protected override Task HandleRequirementAsync(...) { // logic } } Register in DI and use with [Authorize(Policy = "...")].

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.