Today i've noticed that luckperms has many open connections(about 80, yesterday about 150) although i've just got about 15 minecraft servers running at the moment. All those connections are in SLEEP.

Is it possible that LuckPerms isn't closing DB-Connections properly?

They should be active while the servers are online. That's expected behavior. One instance spawns 10 connections.

Aah, ok thanks for the fast response :)