Yeah, you can do Twitter on a weekend… if you only use it yourself and a few friends.
But we are talking about a platform with millions of users, all of which want real-time access to tweets written from anywhere in the world, including image and video content. Just getting to “no outages” and “low enough latency” parts is going to take a lot of effort to build from scratch. Don’t underestimate the complexity of Twitter.
I bet mastodon doesn't have thousands of very active committers. They are taking a lot of users right now. With a hacked together pile of ruby and javascript. Easy to forget that that is how Twitter once started out as well. The bloated org chart came later.
But also, how much time did Whatsapp have to get to that point? I'm not saying it's impossible, but that it's difficult and takes a lot of effort that shouldn't be underestimated.
> They are taking a lot of users right now.
And still less activity than Twitter, and with federation, and with some servers already locking new account creation (mastodon.social, the biggest one, doesn't let you create new accounts).
Again, it's not that it's impossible. It's that it's hard.
The scale of Twitter is large but not enormous. Basically a few trillions of messages overall. Most of them pretty small. All of them immutable (well so far). And lots of images/videos with some CDN in front of that. It's a lot of bytes but not a whole lot of complexity. And a couple hundred million users and user profiles. I can think of a quite a few ways of dealing with all that.
What's hard is things like algorithms and good search. But that's a space where you can achieve a lot with a small and focused team with access to lots of hardware. And obviously this is also something where Twitter has maybe been a bit underwhelming and struggling. User growth and engagement stagnated years ago for them. This was not a healthy social network. It's not like they were nailing this. Throwing more people at the problem wasn't working.