Your question is Securing APIs. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
How do you ensure the security of an API?
Provide a practical, layered design covering authentication, authorization, transport and data protection, input validation, abuse prevention, logging, monitoring, and incident response. Name concrete controls and explain how you would verify that each control works.