We tested out two scenarios:
100 TPS search traffic was pointed to one index
20% CPU usage in data nodes and Threadpool search queue spikes observed. Application side there was increase in TP90 by 3x
80-20 TPS search traffic pointed to two indices
CPU was at 4% with no spikes and no Threadpool search queue spikes observed
Both indices have same number of shards and replicas.
Can anyone help understand why CPU spike behaviour is seen (same load) with to one index vs two indices?