System designHardsd-g046

Subject Cache invalidationLevel Senior–Staff~45 minCommon in Databases & SQL · Distributed systems interviewsIndustries Technology, Software development

Question

An e-commerce catalog service caches product price + availability in a multi-region cache (one cache cluster per region, 5 regions). A price change must propagate everywhere within ~10 seconds, and you must never serve a stale-cheaper price after the change is acknowledged. Writes happen in one primary region. Design the invalidation pipeline and explain how you handle out-of-order invalidation messages and a region whose invalidation bus is temporarily down.

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.