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Comment by ajtulloch | Hacker News Reader

An interesting historical note is that Facebook's chat system was originally written in Erlang (https://www.facebook.com/note.php?note_id=14218138919), before being replaced with a C++/Java system.

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I am more interested in why they switched away from Erlang, that is the opposite of the usual story.

They had trouble finding/training enough Erlang engineers.

Tell me about it!

I used to work for a company that built it's main business product in Erlang. It worked well as product, but business wise hiring engineers was the hardest part. It wasn't helped that they are based in London, where a certain consultancy snatches pretty much anyone who lists Erlang in their CV.

It's hard to believe Facebook can't find Erlang engineers. May be their interview process got in the way. If you use standard algorithm/datastructures interview questions to hire Erlang devs you will have a hard time. All normal data structures in Erlang are immutable and algorithm complexity is a controversial topic there. Using Mnesia/ETS is a bit of a taboo for interviews (like using SQL on your coding task in a C/Java interview). Many Erlang devs would dismiss such questions as irrelevant and try to move on asap which is a big no-no in interviewing.

ETS/DETS are mutable hashtables FYI.

> ETS/DETS are mutable hashtables FYI.

An immutable disk persistence mechanism would be a strange thing.

Sorry, but any good programmer will know the conventional data structures and algorithms, regardless of whether they write programs in Erlang, C or some other language.

It's not about knowing, it's about relevance. These data structures do not exist in Erlang in the same way. So when they ask you to code a snippet to implement a HashMap in Erlang, that will be a pretty insane task.

That is a bad bias. "Data structures & algorithms" could be a footnote in the history of a developer, plus, which "data structures and algorithms" will you use to hire one? The ones relevant to a erlang dev are not the same to a C/embeded one.

I've never seen the point of these questions. Yes I learned half a dozen sorts in college. But in my professional career I have done sorting exactly one way: ORDER BY. Ask me something halfway relevant...

i was headhunted and interviewed for an erlang position (working on chat). i 'failed' a technical interview when my interviewer insisted i provide sample code in php, python or c++. i offered erlang, c, ruby or js and he dismissed me

Check these guys for example http://yuilop.com/intl/lead-server-core-developer-javaerlang... . Look at the challenges they have. These are well known classic problems that generally require mutable lookup tables among other things. Doing it in erlang "to be executed as fast as possible" is crazy.

So many companies and hiring managers get hiring wrong. This is a classic example.

Bob Ippolito answers: http://erlang.org/pipermail/erlang-questions/2014-February/0...

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