If no solution to be able to manipulate (in this case: purge) eqiad MC caches from fenari, I could change all cache keys to use a different prefix.

This would result in new caches to be used and populated. I'd rather not do this though, since the left-over, unused keys are all permanent (do not expire)

[Making bug summary more specific, to differentiate from bug 46423]

(In reply to comment #0)

A maintenance script to purge caches exists:
extensions/ArticleFeedbackv5/maintenance/purgeCache.php. It can not be used
though, since mwscript runs against pmtpa memcached servers & web requests
eqiad.

Note: Aaron stated in https://bugzilla.wikimedia.org/show_bug.cgi?id=46428#c16 that "MWScript.php and mwscript are working now after some permission fixes by Peter and after https://gerrit.wikimedia.org/r/#/c/58124/, so I think terbium starting to get usable. I'll probably start running some scripts on it today myself."

If there is something else blocking progress here, could somebody please elaborate what's needed?

That blocker should indeed be resolved & I'll start purging the caches during the deployment window later today.
If all goes well, that should fix it.

(In reply to comment #4 by Matthias Mullie)

That blocker should indeed be resolved & I'll start purging the caches during
the deployment window later today.
If all goes well, that should fix it.

Matthias: Did it? If not, any timeframe?

It did fix it!