System designHardsd-g611

Subject Object storage strong consistencyLevel Senior–Staff~40 minCommon in Databases & SQL · Storage & CDN interviewsIndustries Technology

Question

Design the metadata/consistency layer of an object store that must offer strong read-after-write and strongly-consistent list operations across multiple availability zones. Constraints: a PUT must be immediately visible to any subsequent GET or LIST from any client, overwrites must not expose a stale or torn version, the bucket can hold a billion keys (so LIST must be paginated and efficient), and the bytes themselves are already durably stored elsewhere. Focus on the metadata layer.

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.