Why can't a shopping cart interface run on the Sabbath?
Starting with what I think I understand, my doubtless oversimplified picture of the world was that processes set in motion before the Sabbath could be allowed to continue. For example, I thought it was all right for your thermostat to close an electrical switch and start a fire in the furnace on the Sabbath if it had been programmed beforehand.
An e-commerce site I saw just now said "Checkout will be available at 9:45pm ET Sat night (in 1 hr 6 min) Thank you for your patience while we observe Shabbat. You may still add items to your cart or wish list to check out later."
The server and the shopping cart software were started already.
Is the issue that selling things, even by automated proxy, even if you don't know they're being bought, is not permitted? Or is it something else?