Large scale distributed systems aren&#x27;t that simple. I don&#x27;t know any internal details of Twitter, but from what I&#x27;ve gathered they <i>are</i> trying to hit the kind of QoS you are dismissing. Imagine some celebrity with millions of followers says something controversial: it would be confusing to a lot of people if they start getting retweets or discussions of that tweet significantly before they see that tweet themselves. And that&#x27;s just one scenario.<p>I don&#x27;t know about the 500 vs. 1000 employee question, but Twitter is a big engineering challenge.