Why architecture matters here

SI failures show up as write skew bugs. Architecture matters because MVCC + conflict detection + escalation combine.

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The architecture: every piece explained

The top strip is mechanics. Transaction start. MVCC read. Row versions. Write on commit.

The middle row is safety. Write skew anomaly. Serializable SI (SSI). Dependency tracking. Vacuum + retention.

The lower rows are practice. vs read committed. Application design. Ops — long transactions.

Snapshot isolation — MVCC + read-view + write skew + SSI escalationread your own consistent snapshotTransaction startread timestampMVCC readas-of snapshotRow versionsinsert / delete markersWrite on commitwrite-write conflict checkWrite skew anomalySI vulnerabilitySerializable SI (SSI)escalate + abortDependency trackingread + write setsVacuum + retentionold versions GCvs read committeddifferent readsApplication designexplicit locks if neededOps — long transactions + versionsdetectescalatetrackcleancompareprotectprotectoperateoperate
Snapshot isolation + SSI escalation.
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End-to-end flow

End-to-end: banking transfer. Both txns snapshot balances. SI would allow both to commit even though overdraft. SSI tracks dependencies + aborts one. Application retries. Correct final state.