Currently, CachingCommonsMediaFileNameLookup passes keys (concatenated in getCacheKey()) directly into BagOStuff methods, without using any make*Key() method. This isn’t ideal; it should probably use makeKey(). That said, the impact of this is limited since it looks like CachingCommonsMediaFileNameLookup is only instantiated with a HashBagOStuff (in WikibaseRepo::getCachingCommonsMediaFileNameLookup()), so the key isn’t used beyond that one cache instance anyways.

See also T255116 for the investigation that led to the creation of this task.