CAP theorem
compound.compound. a rule in computer science that says a database can only have two out of three things: consistency, availability, and partition tolerance. It means you have to make a choice about what is most important for your system.
compound. a principle in distributed computing stating that a system can provide only two of three guarantees: consistency, availability, and partition tolerance. It implies that during a network failure, a system must choose between remaining available or ensuring all data is perfectly synchronized.
The CAP theorem explains why some websites go offline during updates.
When designing the new database, the engineers used the CAP theorem to decide whether to prioritize data accuracy or constant uptime.
Architects of distributed systems must navigate the trade-offs dictated by the CAP theorem, often sacrificing immediate consistency to ensure the high availability required by global user bases.
An initialism formed from the terms Consistency, Availability, and Partition tolerance. The concept was first proposed by the computer scientist Eric Brewer in 2000.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
Usually used with the definite article 'the'.
Last updated July 22, 2026