What the CAP Theorem Says
The CAP theorem states that it is impossible for a distributed system to simultaneously provide all three of the following:
- Consistency (C)
- Availability (A)
- Partition tolerance (P) In practice, partitions (network failures between nodes) can and do happen. So we usually treat partition tolerance as a given: the system must keep operating despite partitions. That leaves a choice: when a partition occurs, do we favor consistency (CP) or availability (AP)? We can't have all three at once.