MediaWiki's SiteStore can be cached and stored in a flat file,
in a json format. If the SiteStore is frequently accessed, the
file cache may provide a performance benefit over a database
store, even with memcached in front of it.

Configuration:

File-based caching can be enabled by setting $wgSitesCacheFile
to the file path of the cache file.

The file can then be generated with the rebuildSitesCache.php
maintenance script.

Format:

In the sites cache file, sites are listed in a key-value
map, with the key being the site's global id (e.g. "enwiki")
and a key-value map as the value. The site list is wrapped
with in a "sites" key.

Example:

"sites": {
	"aawiktionary": {
		"globalid": "aawiktionary",
		"type": "mediawiki",
		"group": "wiktionary",
		"source": "local",
		"language": "aa",
		"localids": [],
		"config": [],
		"data": {
			"paths": {
				"file_path": "http:\/\/aa.wiktionary.org\/w\/$1",
				"page_path": "http:\/\/aa.wiktionary.org\/wiki\/$1"
			}
		},
		"forward": false,
		"internalid": 2666,
		"identifiers": []
	}
}