Oh it's okay, it's a single-player game, it's not that you need any server capacity for that. Other than download servers but it's Steam's problem, not publisher's.
They have a cross platform save sync service which has been disabled, but it sounds like that wasn't load related. I'm not sure how big the save games are but 700k people mashing the quick save button every 30 seconds probably adds up.
I have a total of about 75 saves: quick and auto saves are limited to a rolling 25 by default, plus about 25 manual saves. Steam shows I have used 795 MB of space, so they're not _big_ but they're not small.