Caching is one of the most effective ways to speed up web server performance and by delivering the pages of site in a speedy manner increasing your user satisfaction. In short, it works by keeping a saved copy of any rendered pages in a quickly accessible storage and delivers the page without firing up the wordpress core and all the plugins. That saves the time to re-render pages and content is delivered quickly.
Unfortunately this increase in speed comes with some disadvantages, too. For one it can happen that when you have changes in your content, visitors are still seeing older cached content. Next there might be problems with dynamically created content. And last but not least the FastMember Affiliate system relies on some data being passed to wordpress so it can save affiliate information in a cookie and the wordpress database. This is is done by adding so called GET parameters to the address. GET parameters are the command pairs that you sometimes see trailing a URL after the question mark (like domain.com/?parameter=test).
Now fortunately most wordpress caching plugins have some mechanism to cope with that. Basically they have a setting that tells the plugin not to use caching when a request with GET parameters is detected.
In WP Super Cache the setting can be found in the “Advanced” section of the plugin settings and is called “Don’t cache pages with GET parameters. (?x=y at the end of a url)”
In ZenCache the option is called “GET Request Cache Exclusion”.
If you are unsure whether your caching solution works with FastMember or can contribute options/settings in other plugins, please contact FM support and tell us about it, then we can add to this article.