Elasticsearch is a distributed system. As per the CAP theorem, it can satisfy any 2 out of 3 properties. Which one is compromised in Elasticsearch?
I strongly disagree with Harshit, Elasticsearch compromises on availability as he also mentioned few requests are returned error due to unavailability of shards.
ES guarantees consistency - as data read/write are always consistent. guarantees ES gaurantees Partition tolerance - if any node which was partitioned, joined back to the cluster after some time, it is able to recover the missed data to the current state.
Moreover, there is no distributed system that gives up on Partition Tolerance, cause without a guaranty of PT distributed system can't exist.