Comment by rdtsc
> Java could do it 20+ years ago, just upload your .WAR files to an application server.
Erlang could do it almost 40 years ago.
It can be used to upgrade applications at runtime without stopping the service. That works well in Erlang, it’s designed from the ground up for it. I know of a few places that used that feature.
Erlang seems like a joy to use. I feel a slight pang of regret that I haven't (yet) gotten to use it in my career. (I don't quite have the time or energy to play with it during my off hours, but it is on my list for someday.)