Great comment about SaaS, ganafagol. It's running software that you make money from, not code. Code is just the leverage you have over changing the running software. The running service itself is the ultimate "concrete object" that, for generations, software has been moving away from. There has never been a "compute fabric" as robust as the modern cloud, so long-lived mutable data-structures are becoming more common, and will be even more so.

(We try to have our cake and eat it too in an iterated game where the unit of deployment is immutable and reproducible. That game is called devops and more specifically, continuous delivery.)