as @mmarkus  said, I will end with one method related to the wall clock (that returns the current time). About the time-related, it's useful for me to have the duration times because It's difficult to track how many times the time() is invoked for a single transaction (I'm measuring put, get, prepare, commits, etc...). So, it's easier to override the duration() method to return always 1 and check the stats values based on that duration.