This article is fucking amazing. It lays out _exactly_ how to do database changes, codebase changes, and feature flag deployment strategies step by step with code examples in order to practice continuous deployment without downtime or breaking anything.
I've wanted to write this article for years and never got around to it. Now I don't have to!
(Looks like they have a book on continuous deployment coming out soon. I might have to get this for my teams 👀 )
https://oooops.dev/2021/07/30/surviving-continuous-deployment-in-distributed-systems/