Wikitech does not seem to have any information about the Zerowiki setup, which leads to fear, uncertainty and doubt when developers have to touch the code due to a deprecation or other maintenance issue. (mw.org has lots of docs but they seem outdated, hard to navigate and none of it seems to be devops-related.) There should be an outline of the infrastructure and what the various extensions and helper scripts do.

(The specific question that no one seems to be able to answer that led to the filing of this task is: JsonConfig has some code to sync data between wikis, that code is said to be Zero-related, and is executed on the server; but it is unclear if that's actually used for anything or was a preparation for T89838 which did not happen. But it would be good to have an overview in general.)