What is CAP Theorem?

The CAP (Consistency, Availability, Partition Tolerance) theorem states that a distributed computer system can't have all three i.e. Consistency, Availability and Partitioning tolerance at the same time:

• Consistency: It says that all nodes should see the same data at the same time.
• Availability: System should guarantee that every request receives a response about whether it failed or succeeded.
• Partition Tolerance: The system should continue to operate even if an arbitrary number of messages being dropped/delayed by the network between nodes because of some network error.

Cassandra is typically classified as an AP system, meaning that availability and partition tolerance are generally considered to be more important than consistency. You can get a strong consistency with Cassandra but with an increased latency.