Memcache is Object Cache Mechanism which is to store previously executed database quarries in order to reduce query execution time for upcoming database quarries.
Assumption = You are using WordPress or Joomla CMS.
Wish to use : https://wordpress.org/plugins/litespeed-cache/
If I am correct, then...
When you enable Lightspeed cache plugin along with it's memcache feature; it would be more beneficial.
You should not use Lightspeed cache plugin along with memcache plugin; i.e. If you wish to enable lightspeed cache plugin ... first disable and de-activate previous memcache plugin.
Also, make sure that your hosting account has Lightspeed web server[Apache]; else lightspeed cache plugin will not deliver best results.
some features are like double edge sword; be careful with features that you choose to enable/disable.