Thanks Frederick,
I'm trying to implement a directory-based check (md5 of the WordPress ABSPATH)
I'm having issues. Some items never get hits in the cache, and some items are created without passing through my hook. I think you need to hook the w3tc_add_action to a certain hook in WordPress, can you advise which one?
Right now I just have this code below in an mu-plugin I made:
<?php
w3tc_add_action('w3tc_object_cache_key', 'w3tc_better_object_cache_key');
function w3tc_better_object_cache_key($in)
{
$new_key = $in . '_' . md5(ABSPATH);
return $new_key;
}