I think am now "I created content 10 years ago, and it's still entirely relevant, only tools changed" old.
Software Migration Strategies @ Symfony Live 2013 → https://speakerdeck.com/s0enke/software-migration-strategies
Agile Documentation @ Ops Summit 2016 ⇾ https://docs.google.com/presentation/d/1NKVpeQK9dE4EPTLBHD-PZiQM7ZGYeTA6Qkm5CV2fNWU/edit#slide=id.p
Software migration strategies
The architecture and code you write today is tomorrow's legacy. This talks discusses - besides some basics and theory - how you can safely apply big refactorings to your production environments with minimum risk. We will discuss examples of successful and failed migrations, and why this is not only a technical, but also a cultural issue.