Shopping cart consistency tuning
You operate a Dynamo-style quorum store (replication factor N=3 across 3 regions) backing a globally distributed shopping cart. Most operations tolerate brief staleness, but 'place order from cart' must never undercount or drop an item the user just added. Cross-region round-trips are ~120ms. Design the read/write consistency-level policy per operation, explain how you avoid lost writes and ensure the order path is correct, and describe what conflict resolution and anti-entropy you'd run.
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.
Clarify5:00 left
Estimate5:00 planned
Design15:00 planned
Deep dive12:00 planned
Failure8:00 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.