Welcome to your interview.
The question is on your right: Extensible Backward-Compatible APIs. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
How do you design an API to be both highly extensible and backward compatible at Talon.One?