MediaViewer caches most of its API calls but it does not cache calls to the imageinfo API. This was originally due to concerns about editors getting outdated content, but caching for a short period (say, 5 minutes) should still be okay, and could decrease the load from a popular article significantly.

https://github.com/wikimedia/mediawiki-extensions-MultimediaViewer/blob/f7a00750623bf0c6b96ca90df1934ee77448b198/resources/mmv/mmv.js#L50

See also:

• T116840: Cached REST end point for imageinfo requests