In my very early years when discovering coding I remember fantasizing about a system where I could start my creation as very simple endless loop and add to it w

In my very early years when discovering coding I remember fantasizing about a system where I could start my creation as very simple endless loop and add to it without having to stop it what ever would make up an application (... more a coding experiment in logo or basic it was at that time ;) Fast forward almost 30 years: in Erlang light-weight processes are (most of the time) tail recursive functions handling messages... endless loops. Those light-weight processes are running those endless loops. The described module upgrade functionality allows for uninterrupted system upgrades of servers/services in the back-end which btw. is often serious business in production and the cause of the reltool complexities. BUT: the same hot code reloading system allows for very sleek development experience. You start your first version of the service and from there on update the source and the service changes its behavior most of the time with no restart, no lost state etc. (with the help of some monitoring tools source changes can be picked up automagically...) This kind of dev-environment is simply flow-inducing.