If you are seeing a lot of db load AND don't look at internal events, tuning down events to be logged can help. Note that the only way users see events info is in the 'Who's Online' portlet that is often removed in most services.
Here are two lists that can be added to your uPortal overridesContext.xml file in uPortal-start.
First list is if you want to ignore all events. This would be appropriate if you have no custom reporting from the events database. Very few institutions have this.