CAP and PACELC in practice, consistency models, consensus, and what you give up under partition.
3 questions in System Design.
The write committed on the primary and the reload was served by a replica that had not applied it yet. Fixing it means giving that session a read-your-writes guarantee, either by routing its reads to the primary for a bounded window or by carrying the commit position and refusing to read a replica behind it.
Accepting writes on both sides means conflicts are inevitable, so the design choice is who resolves them. Last-write-wins discards an edit by clock accident; version vectors detect the conflict and hand it back; CRDTs merge deterministically but only for the operations they model. Use this conflict resolution answer to show the decision, trade-off, and evidence rather than a memorised definition.
Under partition you either reject requests on the side that cannot reach a quorum, or serve them and accept divergent replicas that need reconciling. CAP's C is linearisability, not ACID's C, and the choice binds only while partitioned.