Sorry - I have no idea, since I've never seen it happen and don't see why it would have any reason to do what you described.

I'd suggest just planning to keep a close eye on things, and if it does spike, watch exactly which SQL process are chewing up all the resources.

If it were me, I'd be doing a simulation before the sale to try to isolate the problem. Perhaps take a full backup of files+database and install on another server , and set up a sale, let it expire, and see what happens. Of course, you'll need to be clicking around in the test store at expiry time in order to trigger and observe things.