Before bring acquired, WhatsApp had what, 30 employees?

How did they do it? I know they used custom BSD servers so that a single box could keep close to 1M TCP connections open. I'm sure with a fixed target to aim for and all scope known upfront a small crack team of devs could do something similar for Twitter.

One-to-one vs. many-to-many messaging. The amount of work you need to do to deliver a WhatsApp message is constant and small -- just route the message to a single recipient's mailbox. The amount of work Twitter has to do to deliver a message grows as a function of followers. One celebrity tweeting another celebrity means you have to deliver the message to the mailboxes of the followers of both -- millions of times more work than WhatsApp per message. In addition, Twitter persists all the messages while WhatsApp doesn't.

This! Everyone keep's saying it's BSD Erlang and jumping on the Erlang train. Fine tools btw, but WhatsApp is super simple compared to Twitter. rolls eyes

The beauty of Erlang/OTP!

Especially if you completely rewrite Mnesia.

I think this post is relevant here: https://danluu.com/sounds-easy/

I mean, obviously there must be a lot more going on inside twitter besides being a massive many-to-many pubsub messaging infrastructure. And frankly twitter can be improved by leaving a lot of stuff out and up to the client app, so it's not entirely unreasonabl?

> In one incident, he wrote, an error caused every user to log in as somebody else each time they refreshed the page.

Gotta admit, this story raised my eyebrow, this wasn't the dark ages of the web. What sort of crazy experimental authentication voodoo were they running?

Instagram has 13 employees when it was sold to FB.

Did any major companies have the technology growing pains that Twitter did - ie Facebook, Google, Amazon, YouTube, Netflix (streaming), Dropbox, etc.?