When the serverStatus command is invoked, its oplog section collects the most recent applied optime and retrieves the first entry from the oplog collection. Because the oldest op is less likely to be present in the WT cache, this may require us to read from disk, and possibly to wait for space during periods of high cache pressure.

Given the frequency with which serverStatus is called for FTDC collection and by the Monitoring Agent, we should consider implementing a separate caching mechanism and fast-path this query to avoid I/O and WT cache contention.