Many MongoDB drivers currently expose events (CommandSucceededEvent say) which provide an elapsed time. However, that elapsed time is the round-trip time, which is not super useful as that can be measured by a programmer manually. It would be neat if there was a way to get the actual time spent by the server on a per-command basis. This data is computed somewhere as it is exposed in Atlas metrics as Execution Time.

There's the explain facility but this is just to get an estimate of a query's cost. I would be interested in knowing how much time the server spent running an actual command. Latency could then be computed by subtracting this value from the round-trip time.