[nijave]

If you're going that approach, I think a lot of databases have facilities for extending outside plain SQL. Afaik Oracle can bind to Java and Postgres has an extension interface

I do tend to agree with API-outside-the-DB pattern. I guess Oracle supports some form of QoS but I don't think MySQL and Postgres do. That means having multiple apps hit the same schema can cause starvation issues

Also not sure how hard it is to monitor user resource usage. That's more important for billing (even if it's "fake" money from 1 department to another)