A query or search process consists of two-phase, the first is the query phase, during which the cluster distributes the request to each shard (either primary or replica) within the index. During the second, fetch phase, the results of the query are gathered, compiled and returned to the user. It is important to know the rate at which the system is processing requests and how long each request is taking.
There are numerous things that can affect your query performance such as poorly constructed queries, improper cluster configuration. Therefore, we have query operation and query latency metrics to detect such problems in the cluster. If there is a spike in any of these metrics or any emerging trends which might indicate problems in the cluster. You can reach our support center for help.