Multiple ChoiceHard 45s
Dual-write migration correctness
During a DB migration you dual-write to old and new stores but observe inconsistent rows. What is the core flaw of naive dual-writing?
Options
- 1Dual-writes are always atomic across two systems, so a crash between them cannot leave one store ahead or cause any divergence
- 2The two writes are not atomic, so partial failure leaves stores divergent; backfill plus reconciliation or CDC is needed
- 3Dual-writing doubles latency but guarantees consistency, because writing to both stores in sequence is a distributed transaction
- 4The new store rejects all writes by default, so divergence is expected and needs no backfill or reconciliation between the stores
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