The necessary ingredients to make this work are:
Programs that maintain state in a database or are completely static or in a database. It must be something that can be accessed concurrently so that environments can run in parallel.
A somewhat clean baseline state to start with: usually this is a default operating system image.
A programming language that makes it easy to express transformations of that default operating system image so that it can be configured and have programmes installed in it.
An application layer that listens on some sort of network service. Usually this is a web service served over HTTP or HTTPS.
Some mechanism that supports transparent to the client network failover. Commonly this is done with load balancers who distribute requests two backend servers: if back end server is not responding for some reason, The load balancers just skip over that server as if it weren’t present.

Version Controlled Architectures