Apple payments APIs are the worst APIs I've ever worked with. They're inconsistent, badly documented, have unannounced breaking changes and contain so many gotchas it isn't funny. For example, some of the most relevant data is attached to the response but isn't officially supported and may or may not be correct.

It's not exactly fun to code up payment integrations, and so I was kind of hoping to get it over and done with. But with Apples payment APIs, we needed months of production data to figure out how to use them without shooting ourselves in the foot.

Using the API felt like interfacing with some badly configured eventually consistent MongoDB cluster that a bunch of juniors stuffed full of receipts, using the entirely wrong data model.