Why WhatsApp Only Needs 50 Engineers for Its 900M Users | WIRED

WhatsApp as the ultimate Erlang case study

"Like Haskell, Erlang is a product of the ’80s. Engineers at Ericsson, the Swedish multinational that builds hardware and software for telecom companies, developed the language for use with high-speed phone networks. “Instead of inventing a language and then figuring out what to do with it, they set out to invent a language which solved a very specific problem,” says Francesco Cesarini, an Erlang guru based in the UK. “The problem was that of massive scalability and reliability. Phone networks were the only systems at the time who had to display those properties.”

Erlang remains on the fringes of the modern coding world, but at WhatsApp and other internet companies, including WeChat and Whisper, it has found a home with new applications that operate not unlike a massive phone network. In essence, WhatsApp is a replacement for cellphone texting services. It too requires that “scalability and reliability.”"

Why WhatsApp Only Needs 50 Engineers for Its 900M Users | WIRED