@Lasse Gismo (Friendica Antifa) with "unclaimed items" (stuff that is arriving via relay servers) I am deleting those after 1 day, but rest should be fine.
Do you have the rendertime addon on? How long is the time for the "Database" section?
The "mysql tuner" perl script / tool can give some hinds of what to enhance with the mysql settings. With mytop you can see if there are long running tasks on the DB (that should also be logged but at the moment I don't remember how to do that 😅). Which might help to identify the bottleneck.