First, a couple of disclaimers:
So, without further ado, I looked at some old presentations on Twitter's implementation and scalability. MY EYES! THE GOGGLES, THEY DO NOTHING! Let us remember that Twitter is a service so reliable that its most memorable image is the Fail Whale that appears every time it goes down...
So, in a presentation in the late 2000s, post-optimisation, they were handling 600 requests per second on 8 Sun boxes. That's 75 messages per box per second. Er, great. We best not talk about e.g. the performance expected out of IRC servers, a decade earlier.
The real killer for me was this quote:
For us, it's really about scaling horizontally - to that end, Rails and Ruby haven't been stumbling blocks, compared to any other language or framework. The performance boosts associated with language would give us a 10-20% improvement, but thanks to architectural changes that Ruby and Rails happily accommodated, Twitter is 10000% faster than it was in January.
This sounds really cool, until you realise that IN JANUARY, THEY WERE PROCESSING 3 REQUESTS PER SECOND. I've seen shell scripts with better performance, and they're all multi-millionaires now.
Not that I'm bitter. ;)