Rolling Index

Creates one index to a database deployment in a rolling manner. Rolling indexes build indexes on the applicable nodes sequentially and may reduce the performance impact of an index build if your deployment's average CPU utilization exceeds (N-1)/N-10% where N is the number of CPU threads available to mongod of if the WiredTiger cache fill ratio regularly exceeds 90%. If your deployment does not meet this criteria, use the default index build. You can't create a rolling index on an M0 free cluster or M2/M5 shared cluster.