Welcome to your interview.
The question is on your right: Build Non-Conflicting Booking API. 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 would you write an API to fetch available halls given existing bookings so you do not create scheduling conflicts?