Instead of yml for the residence storage which is prone to breakage and version incompatibilities, store the residence information in a SQL database with support for both MySQL and H2 (file) backends.

Might be a good idea. It may help with corrupt files but it won't help with performance (it may actually hurt it). I am currently running the plugin with just under 1,000 residences and have never had an issue.

Will not be applying databases. It will only hurt performance, and I should be able to fix various breaks with a proper patch.

Yea, current save system works fine performance wise, it just needs a little better error handling and possibly a better backup system in case of corruption.

I know most MC server admins don't have a ton of experience, but I feel backups to protect against problem falls outside of plugins. It should be something being handled on the server as a whole.

Very true, I guess I should just focus on weeding out any bugs in the system itself, although I too have never had any problems with it. Most of the issues I've seen from other people was actually YAML failing to handle certain characters appropriately when saving. Don't know if this has been fixed or not yet...

Yeah it is not needed. I am now running with more than 1,500 residences on a single server with no trouble at all.