Short duration: network, bad software deploy
Long duration: db. If you break data, it takes a while to unbreak.
Source: Me. My career has been spent managing db's for internet scale sites.
Source: Me. My career has been spent managing db's for internet scale sites.
Screw ups related to data loss are rare (I've been here years and haven't seen one with the DBs that the stuff I work with uses) but failures at this scale tend to cascade a little ways and it takes time to dig out of the hole. They probably have the problem solved but they have to spend a bunch of time synchronizing things and verifying the fix before they press the big red "go live" button.