CAP Theorem and Beyond

Pick two out of three ##

• Consistency - all nodes see all the data at the same time

• Availability - any node can execute read/write operations

• Partition tolerance - cluster continues to operate despite node(s) failure

Realistic choices ##

• CP - Consistency/Partition Tolerance: wait for a response from the partitioned node which could result in a timeout error

• AP - Availability/Partition Tolerance: get the most recent version of the data, possibly stale

• ElasticSearch is a search engine: consistency is at the document level