Your question is Design an API and Ticket Reservation. 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).
Design a system to reserve a ticket (ticketmaster/jetblue/etc.).
Treat inventory and payment as strongly consistent transactional systems, and explain where ML can assist without making reservations unsafe. Cover search and option ranking, availability-aware candidate generation, temporary holds, confirmation, cancellations, and recovery from duplicate or expired requests. Discuss scale assumptions, online versus batch inference, latency, evaluation, monitoring, and failure handling.