The MediaWiki default is to store localisation cache in the database.
At WMF production, it's been the case for many years that these are stored as a file on disk instead, in a private cache directory. MediaWiki offers two well-tested formats for this: php array files, and CDB files. CDB files is what WMF currently uses in production. PHP-array files is what we're moving toward (T99740), which are faster to generate and faster to read than CDB files.
For third parties, this means:
- More performant by default. We'd no longer require db-master connections on web requests when repopulating the localisation cache.
- Better recache performance.
This seems like a fairly easy thing to enable by default. Should we do that? Are there reasons we haven't already?