Manual:$wgLocalisationCacheConf

Details
Localisation cache configuration.

Associative array with keys:

The class to use. May be overridden by extensions. The location to store cache data. May be 'files', 'db', 'array' or 'detect'. This is significantly faster than storing data into the database thread>Thread:Project:Support desk/$wgLocalisationCacheConf performance: file or db storage?|(see discussion) ** If set to "array", data will be in PHP files that store static arrays. This is an experimental option. The class name for the underlying storage. If set to a class name, it overrides the "store" setting. Set this to true to disable cache updates on web requests. Use  instead.
 * class:
 * store:
 * If set to "files", data will be in CDB files in the directory specified by  .
 * If set to "db", data will be stored to the database.
 * This is the fastest option when using PHP-FPM and OPcache (without ), because OPcache will store these arrays. In other configurations (HHVM or opcache.file_cache_only) this mode has no benefit over "files".
 * If set to "detect", files will be used if   is set, otherwise the database will be used.
 * storeClass:
 * storeDirectory: If the store class puts its data in files, this is the directory it will use. If this is false,   will be used.
 * manualRecache: