Other MongoDB products use the ratio or returned vs scanned to indicate healthy queries and good indexes. In certain cases, we alert end users if this ratio is too high (over 1000)

However, since oplog queries are included in this global metric, change streams and the triggers built off change streams cause these alerts to happen much more frequently. Additionally, in the case of oplog queries, the ratio does not indicate a bad query and may just indicate a selective change stream. These alerts are not at all actionable in these cases.

The solution is to remove oplog queries from the scanned and returned counts and add a new metric which includes the oplog queries.