System designHardsd-g204

Subject QuorumLevel Senior–Staff~45 minCommon in Databases & SQL interviewsIndustries Technology, Software development

Question

Design the storage layer for a globally distributed shopping-cart service (Dynamo-style) replicated N=3 per key across regions. The product needs 'always writable' carts (adding an item must never fail even during a network partition) but checkout must read a consistent view of the cart. With per-request tunable R and W, how do you set quorums for the add-item path vs the checkout path, and how do you handle a node that's down during a write?

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.