Not going to lie, Java app servers basically had me predisposed to see the appeal of Elixir. When I was spending a lot of time with Ruby I got really into Torquebox (Ruby-ized JBoss) specifically for the clustering aspects, ability to spread workers and clustered cache with Infinispan.

Elixir has a lot in common, but it takes it to another level. You can call functions from those other applications on the server with nothing more than a Module.function(arguments). You can call a function on another node in the cluster by just sending the node + module, function and arguments.

Because of immutability and message passing, this just works everywhere. With Java, a similar implementation would have to guard against memory references and mutex locks that wouldn't behave the same way on different nodes.