Well if your application has business logic at all you're going to have to write business logic at some point, and I personally like the idea of keeping as much

Well if your application has business logic at all you're going to have to write business logic at some point, and I personally like the idea of keeping as much of it co-located with the data - it makes your schema the SSOT for your data structure and it's constraints and transformations. The complication is as always external services, like sending email, validating IAP receipts, things like that. For that I liked to take some of the principles from the 3factor app devised by the Hasura team, and make them asynchronous, and performed by worker processes (in my case, with graphile-worker).