What you've outlined sounds solid to me... I'm not sure what else you could do. You're right about foreign keys, and if they don't offer an API to revoke licenses then the manual process is what it's gotta be. One thought that occurred to me was instead of deleting the order so you have no record of it at all, you could use an order status like Canceled for these orders. Then just list on a page all the remaining licenses in your table attached to canceled orders. Once the store owner revokes the license manually, he can click a link on that table to set the order ID for that key in the DB to 0 or something.