The CAP theorem is fundamental to understanding distributed systems and NoSQL databases.
The Three Properties
- Consistency: Every read receives the most recent write or an error.
- Availability: Every request receives a (non-error) response, without the guarantee that it contains the most recent write.
- Partition Tolerance: The system continues to operate despite an arbitrary number of messages being dropped/delayed by the network.
Rule: In a distributed system (P), you must choose between C and A.