Manual:$wgLocalisationCacheConf/de-formal

Details
Localisation cache configuration. Associative array with keys:

This is significantly faster than storing data into the database (see discussion)
 * class - The class to use. May be overridden by extensions.
 * store - The location to store cache data. May be 'files', 'db', 'array' or 'detect'.
 * 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.
 * If set to "array", data will be in PHP files that store static arrays in the directory specified by . This is an experimental option.
 * 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", CDB files will be used if  is set, otherwise the database will be used.
 * storeClass - The class name for the underlying storage. If set to a class name, it overrides the   setting above. Built-in options: LCStore interface on doc.wikimedia.org
 * 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 - Set this to true to disable cache updates on web requests. Use instead.