Distributed checkout saga coordination
Design the checkout flow for a travel-booking platform where one purchase must reserve a flight (airline API), book a hotel (hotel API), charge the customer (payment service), and issue loyalty points (loyalty service) — four independent services with their own datastores, no shared transaction. If any step fails, the whole booking must unwind cleanly with no orphaned charge or held inventory. Volume ~3,000 bookings/sec. Describe how you coordinate this without a 2PC and how you guarantee consistency and exactly-once effects under retries.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify6:00 left
Estimate6:00 planned
Design18:30 planned
Deep dive14:30 planned
Failure10:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.