I like the simplicity advocated by Pieter Levels. The fact that he uses PHP with PHP-FPM solves the problem of deploying a new version (starting the new versio

I like the simplicity advocated by Pieter Levels. The fact that he uses PHP with PHP-FPM solves the problem of deploying a new version (starting the new version, switching new connections to the new version, draining existing connections, stopping old version). But when using a single host machine, you still have the issue of updating the kernel and the OS, and this is sometimes better done in an "immutable" way, by setting up a new VM and switching traffic to it. This is where things become a bit more complex. You have to use things like AWS EBS or Google Cloud Persistent Disk, detach them from the old VM and reattach them to the new VM. You also need to use floating IP or a load balancer. In other words, baby-sitting the machine and its OS, either done manually or automatically, is a real pain. Maybe the real simplicity lies in using something like Google App Engine, Heroku, Clever Cloud or Scalingo.