We don't use SQL as the authoritative store of business state. We use C# types and all the code that goes around them for most of our heavy-lifting.

We map our C# domain model instance into a SQL database (SQLite in-memory) each time we want to execute business rule SQL against the state. These databases are ephemeral. For some interactions, we might generate 5-6 of them per user action. It is very fast to do this when your row counts are low (i.e. projections per user or per user transaction).