Principle

CAP Theorem

During a network partition, a distributed data system must choose how it trades off consistency and availability.

CAP is often oversimplified into a slogan. Its real value is as a forcing function: what behavior do we prefer when communication is unreliable?

Where This Connects

A distributed system is a system made of independent components that communicate over a network to behave like one useful whole.

Consensus is agreement under uncertainty: multiple participants decide on one value even when messages and machines may fail.

A way to reason about engineering choices where improving one property changes cost, complexity, risk, or behavior elsewhere.

A way to reason about engineering choices where improving one property changes cost, complexity, risk, or behavior elsewhere.