Hi, folks!
Recently we have upgraded our deployment from 4.2 to 6.0 (community).
We back up using periodic filesystem snapshots and more frequent oplog tailing.
On 4.2 these oplog dupms caused periodical CPU peaks. However, after upgrading to 6.0, these peaks mysteriously disappered. (Yes, we have checked our cron jobs 
. Backups are running.)
Does anyone have an idea what could be behind this? Is there some secret index on oplog?
Thanks for any hints 
P.S. I’m not showing off, I’m just curious