How to reliably consume S2S IAP items from a user's inventory

Hey! We ended up accepting the risk here that in a failure corner case, we would end up consuming the consumable and not creating a corresponding record. We create records locally when we go to consume the consumable, which leaves enough of a paper trail to handle any broken transactions on a case by case basis. It should be mentioned, as long as that gap from when you issue the request to consume the item and create the corresponding artifact on your system is as narrow as possible (and contains as little behaviour as possible) it should be an outside chance that it ever happens even with decent traffic on those endpoints. (we've never had it happen personally)

As for chargebacks and voided transactions, I think meta does their own auditing on their purchasing systems so in general you can assume that you don't need to handle those cases directly.