What makes and clears var/cache/pfilters_c9affdee3

From my cPanel I see a lot of files being created that have the name pattern as follows : var/cache/pfilters_c9affdee3a4e2fc46d9af5f4c1846aa0

When I use admin.php?cc they are removed, but rebuild quickly to as many as 5,000 to 20,000 inodes.

Does anyone know why this many files would be created and where in the script these cache files are created and cleared ?

The number of files being created with this name pattern seems excessive to me, since other cache files seem to be created in much smaller numbers.

Have I missed some setting somewhere ?

2.1.4 PRO

Product filters. They are created on first access. So if you have a filter block, they will be created on demand. You might consider using sqlite cache_backend in config.local.php