Erlang Factory 2014 - That's 'Billion' with a 'B': Scaling to the Next Level at WhatsApp

Not sure why this comment saw a couple downvotes earlier. mbesto is correct: for most startups, most of the time, competitive advantage doesn't come from the underlying tech stack. To make a general statement, most things could be done similarly on any of several platforms. However, when product requirements match exceptionally well with a specialized technology, you can see things that would simply be infeasible or extremely tough using a different stack. WhatsApp + Erlang was one of those cases (watch this talk and imagine trying to recreate that system with only a handful of server engineers using any other tech: [this video] ). Discord + Elixir appears to be another. Curious if anyone has any examples that spring to mind from outside the highly concurrent messaging space.

It's required because your phone is where your messages are stored. Whatsapp don't retain messages/media after they've been delivered to your phone, which is a compelling privacy feature for many. It's also what allows them to serve such an enormous user base with limited hardware. Their technology stack (FreeBSD/Erlang) is pretty interesting, more info here: 2014 talks by Rick Reed: [this video] [link] Slides: [link] There's likely no technical reason why you couldn't use a pc instead of a phone for users that want to use the pc as the primary client (with the phone optionally accessing the DB on the pc in the same way that the desktop client does for the phone). Perhaps they've decided that this is a small and declining market. Edit: Slides for second talk [link] 440k connections/sec, 1.1 million msgs/sec, 1 billion images/day, and that was in 2014...

I believe the issue is that unlike web chats and apps like Telegram, Whatsapp doesn't store conversations on their servers beyond what is required to deliver messages to the required destination device(s). This presents obvious problems with having not just a web client, but any client other than the main device, since the main device is the only store of the existing conversations. New messages sent also need to be synchronized across devices, which I presume is why it's required to keep your phone connected to the Internet. Otherwise Whatsapp would need keep conversations on their servers until they could be synced, which is very much not their model. Details on their architecture: [this video] [link]

Klarna (the European payment processor) and WhatsApp architectures are built on Mnesia. Mnesia is Erlang's built-in distributed database. Due to its age it has a few bad corner cases, that could be fixed if it just had a better backend (the front-end API is nice, well designed, supports transactions, is built-in to the lanauge). So this effort brought in the ability to have a better backend, and make Mnesia a better option as a general purpose distributed database. Here is an talk on how WhatsApp uses Mnesia: Erlang Factory 2014 - That's 'Billion' with a 'B': Scaling to the Next Level at WhatsApp [this video] Here is an example of using Mnesia: [link]