Due to known security issues with using memory caching services like memcached or redis on shared servers, we do not use memcached to improve performance on our shared servers. You are welcome to use it or redis on a VPS. For WordPress on shared hosting we use and recommend (and pre-install) the free file-based object caching solution Docket Cache. You can read more about the utilities we use for performance improvement in the "What makes us better..." section above, including custom nginx rules to work with common WordPress caching plugins and the option to enable nginx level caching.