Cassandra Database — CAP Theorem
CAP Theorem stands for Consistency, Availability and Partition Tolerance. It was proposed by Eric Brewer in 1999. It is the basis theorem for distributed databases.
CAP theorem is a concept that distributed database systems can ONLY have 2 of the 3 concepts. It is not possible to have all 3 concepts simultaneously.
Consistency
The same data must be available in all nodes in the cluster at the same time.
Availability
Every request must get a response whether it has succeeded or failed.
Partition Tolerance
The system continues to run without losing messages. If part of the system has failed, it does not affect the entire system.
Cassandra falls in the “AP” (Availability and Partition Tolerance) intersection of the CAP Theorem.
In other words, Cassandra is a best fit for a solution seeking a distributed database that brings high availability to a system and also is very tolerant to partition to its data when some node in the cluster is offline (which is very common in distributed systems).
