You cannot get everything! Specially, out of distributed system!

CAP theorem (Brewer’s theorem) :
It is impossible for distributed computer system to simultaneously provide all three of the following guarantees:

Consistency: There are many way to describe it
* All nodes see the same data at the same time.
* Once a state is stored in the system, it will report the same state in every subsequent operation until the state is explicitly changed by something outside the system.
* A service that is consistent operates fully or not at all.
* In other way to say, atomic-ness is built-in to service.
The degree to which a system is operable and in a committable state at the start of a mission, when the mission is called for at random
* Node failures do not prevent survivors from continuing to operate
Partition Tolerance:
* The system continues to operate despite arbitrary message loss
* No set of failures less than total network failure is allowed to cause the system to respond incorrectly

In other words, though it is very desirable to have Consistency, Availability and Partition-tolerance in distributed system, unfortunately
no distributed system can achieve all three at the same time!


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