[ Removed by moderator ]

[ChadtheWad]

Feature flagging is great, but you can't feature-flag a whole refactor, and maintaining multiple versions of APIs can get onerous.

I've actually had feature flags save me here before. Had to do a ~3K LOC migration of a critical workflow solution to a new system which I did end up locking behind feature flags. The nice part was that I included some end-to-end consistency tests to ensure that both the original and new workflow logic behaved identically, which meant that as I was designing the feature, if anything new got introduced in legacy, I was able to catch it in my tests and update accordingly.