Even totally dodging docker/k8s/nomad/dagger or anything that's even remotely complicated platforms like AWS/DO/Fly.io/Render/Railway/etc obsolete this "simple" approach with nothing but a config file.
I also theorize that the author is likely wasting a boatload of money serving ~0 requests on the staging machine almost all the time, due to him literally switching a floating IP rather than using two distinctly specced machines for production and staging