> Also typical database uses 96% of the time for logging, locking etc. and 4% percent for actual data operations

That's a strange claim, in my work it's always been 100% data ops.

> “Letting people connect directly to the database is a madness” — yes it is.

why?

> Killing database by multiple connections from single network port is simply impossible in real life scenario. You will long run out of free ports

Depends entirely on the workload. And it's very possible. All too entirely so.