CAP under partitions: a precise consistency tradeoff
Research context
theory comparison · established · As of 2026-10-10
In Gilbert and Lynch's asynchronous read/write model, an implementation cannot provide both atomic consistency and a terminating response to every request at every nonfailed node during arbitrary partitions.
Key knowledge
In Gilbert and Lynch's asynchronous read/write model, an implementation cannot provide both atomic consistency and a terminating response to every request at every nonfailed node during arbitrary partitions. An isolated replica cannot always know the latest write while also answering every request. Changing the operation contract, permitting rejection/unavailability or weakening consistency changes the guarantee. CAP is not a permanent instruction to choose any two qualities for every system.
Conditions and scope
- Consistency here is atomic/linearizable register behavior and availability is the paper's per-request termination condition.
- Partition behavior and allowed response errors must be explicit; ordinary latency and practical uptime are different measurements.
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Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: Definitions and asynchronous atomic read/write impossibility theorem; partial synchrony discussion. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
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