My Understanding of the CAP Theorem

With the technical landscape being distributed, you will have heard of the CAP Theorem, as it related to the systems that you work on to be 99.99999% up. These are my $0.02 on my understanding of the CAP Theorem.

* Consistency – read/write guarantee between nodes
* Availability – nodes respond and do no error out
* Partition Tolerance – system still functions when network goes berserk

Let’s face it: networks are unreliable. Period. So, the theorem states that you can only really guarantee 2 out of the 3 above, specifically:

CP – consistency and partition tolerance
AP – availability and partition tolerance

The difference is which one to to choose, and it all depends on your business requirements.

* CP when requirements dictate atomic read and writes
* AP when data consistency is flexible around data synchronization

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