i'm not doing databases for living but the idea of stringifying a perfectly cromulent unique number in order to store it in the database comes as slightly weird to me.

If you’re using a new-to-you ORM, and you don’t ever check the docs to see the basic primary key syntax… it’s SQLAchemy, it’s well documented and there’s tons of prior art.

Also I don’t understand their business case but if a user has a primary key, a unique user ID, and a unique customer ID, then all three of those uniquely identify the customer. (Weird, but there are some plausible explanations.) But then why would you need both the user ID and the customer ID in the subscription table is this some stripe thing I don’t understand or are they just bad at this?