>Object caching is php, not directly related to the database server.
you meant opcode caching
Object caching is related to query caching by using wordpress transients api (http://codex.wordpress.org/Transients_API) and can use
Memcache (recommended for big servers)
Xcache/APC/APCU (for small servers)
via separate plugins (Tribe cache plugin has all-in-one collection)