For a few months I tried to find the reason why some customers of our Advanced Ads plugin ping our website multiple times per day to check for plugin updates even though they should do this only once per day. I finally found out that this not only hit us, but is a large problem to everyone using W3 Total Cache.
WordPress update checke
WordPress is checking for updates of the Core and plugins with wordpress.org every 15 (?) minutes when you are in WP Admin. This is why you get update notices very quickly.
The result of the check is saved in a so called transient, basically an option with an expiry date. After 15 minutes this option expires so WordPress knows that it should check again.
W3 Total Cache Object Cache is breaking transients
W3 Total Cache has an option called Object Cache. I found out that whatever method you activate, it seems to break transients. Maybe this is not true for every site, but every one I checked it on and a lot of our client’s or else I would never have started to look for it. Worse case, it causes problems on the over 1 Mio pages where this plugin is installed.
“Breaking transients” means that the transient is always empty which causes WP Admin to check for core and plugin updates on every page impression in the admin area. The same applies to our own premium plugins and many other plugin or core features using transients, too. I helped Easy Digital Downloads to fix this quickly, too.
If you have W3 Total Cache installed and Object Cache activated, this likely hit you, too. If not and you know about a limitation I didn’t find out about, please let me know in the comments.
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What can I do about this?
You could switch off the Object Cache feature. I can not tell you though how big the impact on your site’s performance will be.
Please contact the plugin developer to put more pressure on a solution.
Or use a better, more stable and user friendly caching plugin. I personally suggest WP Super Cache to new and very small sites and WP Rocket to sites that are serious, make money or love good support.