[conradfr]

Yes, that's a problem, you can't be the only one responsible for a core part of the stack.

I did an interview at a major streaming company and one critical part was written in Erlang. It has been working great but the guy who wrote it had left for some time and nobody knew Erlang there, so they would have to rewrite it if an update was needed.

[toast0]

Or, someone could take a week to learn Erlang and make whatever change is needed. You won't be an Erlang expert in a week, but it's a pretty small language, so editing existing code isn't that hard. And that existing code can't be that bad, since it's still working.