PACELC Extension¶

CAP only describes behavior during partitions; normally, systems trade consistency for latency - PACELC captures this: "if Partition, choose Availability or Consistency; Else, choose Latency or Consistency."

Tension Addressed¶

Consistency vs. Latency

Recognizable As¶

Tunable consistency levels (eventual, session, strong); read-your-writes guarantees; synchronous vs. asynchronous replication choices; latency vs. durability configuration

Canonical Sources¶

Abadi, "Consistency Tradeoffs in Modern Distributed Database System Design" (2012)

Transfers To¶

Database tuning, replication strategy, globally distributed systems, real-time systems

This extension explains why many distributed databases offer consistency levels as configuration - it's not a failure of design but recognition that different use cases have different tolerance for staleness vs. latency.