Question

Under the CAP theorem, if a distributed database prioritizes Availability and Partition Tolerance, which property must be sacrificed during a network split?

Accepted Answer

Under the CAP theorem, a system that prioritizes Availability and Partition Tolerance must sacrifice Consistency. The CAP theorem states that a distributed data store can only provide two out of three guarantees simultaneously: Consistency, Availability, and Partition Tolerance. Consistency means that every read request receives the most recent write or an error. Availability means that every request receives a non-error response, regardless of the individual state of nodes. Partition Tolerance means the system continues to operate despite an arbitrary number of messages being dropped or delayed by the network between nodes. A network partition occurs when communication between nodes in a distributed system fails, effectively splitting the system into two or more isolated segments. If the network splits, the system is forced to choose between keeping the system reachable, which is Availability, or ensuring all nodes show the same data, which is Consistency. If you choose Availability and Partition Tolerance, the system will allow reads and writes to proceed in both segments of the split network, but because the segments cannot communicate, they cannot synchronize updates. This leads to a state where different parts of the system return different versions of the data, meaning Consistency is sacrificed.

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Under the CAP theorem, if a distributed database prioritizes Availability and Partition Tolerance, which property must be sacrificed during a network split?