I'm trying to figure out whether Synthetic Full will be reasonable with Glacier storage class. Does anyone have a sense of what is going on behind the scenes?

Is it just marking the old base version and increments as deleted and then uploading a complete new base version of that particular file? If so, this should not trigger any Glacier requests, right?

Or is there something more complicated going on?

I was thinking of doing incrementals daily, and then Synthetic Full every two weeks. I don't mind having a 4 hour Glacier request delay once every two weeks, if that is what is needed. But I'd rather not be paying for tons of requests.