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Comment by mtw | Hacker News Reader

Good question is why oh why switch WhatsApp to Facebook tech when it was running perfectly ok on its own. Never crashed.

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So that engineers can be moved between product groups while carrying relevant knowledge and experience with them.

I'm pretty sure a bunch of Erlang programmers being shoehorned into a PHP codebase is the literal definition of Hell for all parties involved.

Facebook is not a “PHP codebase.” I’d guess that fewer than 0.01% of CPU cycles at Facebook are used by PHP.

Isn’t a significant amount of the codebase in Hack, a PHP derivative?

C++ is the most popular language at Facebook, I know that one for sure. They used to run PHP on HipHop VM which was written in C++, but now they transpile PHP to C++.

The transpiler is HipHop. They discontinued that in favor of HHVM, which does JIT compilation instead. More info: https://hhvm.com/

EDIT: apparently, though, HHVM stopped supporting PHP itself last month; now it only supports Hack. I'm not familiar enough with Hack to know how much it actually deviates from / improves upon PHP.

If that’s the goal, why not start incorporating more Erlang into the rest of Facebook instead? It proved its mettle at WhatsApp.

Facebook has to hire thousands of engineers per year. They may incorporate more Erlang into Facebook, but they have to have a core tech stack that can easily onboard engineers from a variety of backgrounds. I don't have the foggiest idea of whether Erlang can be part of that or not, but people talk about it as if it's a special-purpose tool.

Facebook was actually using Erlang way before WhatsApp

https://www.quora.com/Why-was-Erlang-chosen-for-use-in-Faceb...

Speaking as an Erlang developer I approve of this question.

The answer should be clear at this point. WhatsApp provided too much privacy and not enough monetisation opportunities.

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