What common mistake do developers make with After middleware logic, why does the mistake cause problems, and what is the safer approach?

What common mistake do developers make with After middleware logic, why does the mistake cause problems, and what is the safer approach? One recurring problem with after middleware logic is applying it without understanding the boundary it protects. Putting business-domain calculations into middleware just because middleware runs on every request. In addition, Middleware can also inspect or modify a response after downstream application logic has completed. Safer engineering approach: keep the responsibility in the correct layer, use the framework's supported API, validate and authorize inputs, avoid hidden side effects, and verify the behavior with tests.