System designHardsd-g218

Subject Consistency modelsLevel Senior–Staff~50 minCommon in Databases & SQL interviewsIndustries Technology, Software development

Question

Design the booking/transaction flow for a travel platform where a single 'trip' purchase must reserve a flight, a hotel, and a car — each owned by a different microservice with its own database, possibly in different regions. The whole trip must be all-or-nothing from the user's view (no charging for a flight if the hotel can't be booked), but you cannot run a distributed ACID transaction across these independent services. How do you keep the booking consistent?

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.

Learn the concepts

Narrate your design

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Run or narrate your approach, then ask the coach.