I have 2 clusters.
Cluster A: have 1 big index storing 500 GB of data
Cluster B: have monthly indices of 30GB for 15 months
There is a search query which search over a single index in cluster A and over read-alias [image-2019-10, image-2019-11, ..., image-2021-06] in Cluster B.
According to search latency metrics of Cluster Health,
Cluster B has 4-6 ms of search latency over a shard.
Cluster A as 30-40 ms of search latency over a shard.
But the overall result of the query in Cluster A takes 10seconds and Cluster B is taking 20seconds.
I think Cluster B uses threads internally to search parallely over multiple indices, so overall time taken by search query with alias should be less. Am I missing something?