Manual:$wgMainCacheType

Details
Object cache setting which replaced $wgUseMemCached.

Here are the keys available by default (defined as constants in Defines.php):
 * – Use $wgMainCacheType, $wgMessageCacheType or $wgParserCacheType if they are set to something other than  or  . Otherwise use.
 * – Do not cache (default).
 * – Store objects in the database table objectcache table. Warning: This could potentially be slower than no caching for $wgMainCacheType.

See Manual:$wgObjectCaches for an example of a custom backend (e.g. Redis).
 * – memcached, must specify servers in $wgMemCachedServers.
 * – APC if available. Note: If using, increasing apc.shm_size may improve performance.