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CAP Theorem

CAP Theorem for a distributed architecture:

Consistency: The data in database remains consistent after the execution of an operation.Example: After an insert operation all clients will see the same data

Availability:The System is always On/Available.

Partition Tolerance:The system continues to function even if the servers are not able to communicate with each other

CAP provides the basic requirement to follow 2 of the 3 requirements in distributed system. it is impossible to follow all 3 requirements, so NOSQL DB follows different combination of C,A,P from CAP theorem.

CA: Single site cluster , all nodes are always in contact. when partition occurs system blocks.

CP: some data may not be available but the rest is still consistent and accurate

AP: System is still available under partitioning but some of the data may be inaccurate.

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