I was talking about the client side here, which is maybe a web backend. If it's using threads, at least the connection pool will be thread-safe. If it's event loop, N/A.

If you want to look at the DBMS itself, well typically there's a separate process per connection, but say it uses threading instead... It'd be thread-safe too. You aren't hitting UB by doing concurrent xacts.

Snapshot xact is what I was thinking about. Not sure about Oracle, but in Spanner they can be parallel.