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CAP: a distributed system cannot simultaneously provide consistency, availability, and partition tolerance.
Scope: distributed computing and database systems.
Statement
It is impossible for a distributed computing / database system to simultaneously provide the three:
Consistency
Every read receives the most recent write or an error. This means that the system appears as if there is a single copy of the data, and all reads will return the same value.
Availability
Every request receives a (non-error) response — without the guarantee that it contains the most recent write. This ensures that the system is always up and running, and every query receives a reply.
Partition tolerance
The system continues to operate despite an arbitrary number of messages being dropped (or delayed) by the network between nodes. In essence, the system can withstand network failures.
Updated:
2026 Aug 19
