Definition
The CAP theorem states that it is impossible to design a distributed data management platform that provides always consistent (C) data accessed through always available (A) operations if there is the possibility that the set of nodes may partition (P), that is, where there may be nodes which are unable to communicate with each other.
Key Points
The CAP theorem was stated in 1999 by Fox and Brewer [2], and it was proved mathematically by Gilbert and Lynch in 2002 [3]. The CAP theorem is often used to justify NoSQL data platforms that do not keep data consistent, but rather provide eventual consistency (q.v.) or other weak consistency models for replicated data (q.v.).
A common description of the CAP theorem is that a system can have at most two out of the three properties: consistency (C), availability (A), and partition tolerance (P). However, consistency and availability are properties that the system might choose to offer to users, or not; but P is a property of the...
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Recommended Reading
Abadi D. Consistency tradeoffs in modern distributed database system design: CAP is only part of the story. IEEE Comput. 2012;45(2):37–42.
Fox A, Brewer E. Harvest, yield and scalable tolerant systems. In: Proceedings of Workshop on Hot Topics in Operating Systems; 1999. p. 174–8.
Gilbert S, Lynch N. Brewer’s conjecture and the feasibility of consistent, available, partition-tolerant web services. SIGACT News. 2002;33(2):51–9.
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Fekete, A. (2018). CAP Theorem. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_80644
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DOI: https://doi.org/10.1007/978-1-4614-8265-9_80644
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