I'm using wordpress as a CMS. I've currently got 1500+ categories, and am in the process of adding more, hopefully up to around 10,000 or so. There are about 30ish categories, each having 30ish subcategories, and most of those have/will have more subcategories for a third level.
When adding new sub-categories now, though I can see them immediately in phpmyadmin, there is a delay in them showing up in the wordpress admin ui and/or the website itself. Sometimes it takes five minutes, sometimes hours, and then all of a sudden the new categories will appear in the wordpress admin interface.
I have the latest version of wordpress, apache, mysql, and php. I've disabled all plugins, but to no avail.