Manual:$wgObjectCaches

Details
Advanced object cache configuration.

Use this to define the class names and constructor parameters which are used for the various cache types. Custom cache types may be defined here and referenced from $wgMainCacheType, $wgMessageCacheType or $wgParserCacheType.

The format is an associative array where the key is a cache identifier, and the value is an associative array of parameters. The "class" parameter is the class name which will be used. Alternatively, a "factory" parameter may be given, giving a callable function which will generate a suitable cache object.

Custom cache types
You can also create other cache configurations in addition to the built in CACHE_ constants by adding them. For example, to use redis as your cache (which does not have a built in CACHE_XXX constant) you can do: