UBB.threads just a simple system that reads/writes data to the backend and displays it to the browser via a simple select statement. There are two features one really has to worry about with UBB.threads in regards to system load, these two options are:
- Show Total # of Unread Replies in Topics
- Show Total # of Unread Posts Per Forum
Their description is as follows:
Warning: This can cause excess load and contribute to slow speed.
I just logged in at your site and they don't appear to be enabled. FWIW I've seen 10gb db usage on some super large UBB.threads installs, as long as the system resources can support the database/webserver then everything will work fine.
You will want to keep up with the latest posted maximum supported PHP build with each version, the newer the PHP build the faster results you'll have. If you're still stuck on PHP5.4 you'll have a much faster experience on the latest PHP7 builds. We are currently working on PHP8.1 support and will, eventually, drop support for PHP5 at some juncture in the future.