A succinct problem statement to give context for why the review was initiated.
This extension has been deployed to prod around seven years ago and after a while it became virtually without any maintainer, Technical debt in this code is unimaginable and in matter of UX/UI it's non-standard and out-dated but any (of my) attempts to to modernize it failed due to out-of-date and non-standard php code.
Number, severity, and age of known and confirmed security issues:
Was it a cause of production outages or incidents? List them.
Found this: https://wikitech.wikimedia.org/wiki/Incident_documentation/20170111-multiversion but it might be not that related
Does it have sufficient hardware resources for now and the near future (to take into account expected usage growth)?
No, given the nature of the extension, it's very unlikely it will need more hardware any time soon.
Is it a frequent cause of monitoring alerts that need action, and are they addressed timely and appropriately?
The extension is a frequent cause of problems like PHP errors and PHP fatals (such as T174803).
When it was first deployed to Wikimedia production
- In mid-2008 to de.wikipedia.org. (Per https://meta.wikimedia.org/wiki/Flagged_Revisions)
- In late-2010 to en.wikipedia.org (According to this)
Usage statistics based on audience(s) served
More than 45 Wikimedia projects.
Changes committed in last 1, 3, 6, and 12 months
Reliance on outdated platforms (e.g. operating systems)
Number of developers who committed code in the last 1, 3, 6, and 12 months
Number and age of open patches
Number and age of open bugs
Number of known dependencies?
The configuration page mentions Echo, Scribunto and some other WMF extensions
Is there a replacement/alternative for the feature? Is there a plan for a replacement?
There is no replacement or alternative mapped or planned. One option would be to undeploy this from production. However, doing so would remove the ability for communities to protect pages in a way that still allows contributions. (In other words, it removes the ability to perform pre-publish edit review.)