Two years ago at CodeMash we discussed how Erlang was a paradigm shift masquerading as a programming language. Last year we illustrated how fun it is to write. This year we show off one of its most powerful aspects: maintaining a production system.
Erlang (and Elixir, its younger sibling) allow you to not only trace the behavior of a production system, but also to query the data in memory, replace your code on the fly once you've found the problem, and fix the data that the old code mishandled, so the system keeps plugging away. Look, ma, no reboots.
Also discussed will be other criminally under-appreciated languages with similar features, because really, can you ever have enough magic tricks in your repertoire?