First of all, their infrastructure is globally distributed. This was one data center of many. Second of all, this isn't just '140 character tweets'. It's image

First of all, their infrastructure is globally distributed. This was one data center of many. Second of all, this isn't just '140 character tweets'. It's images, video, data being sent at staggering speeds because people tweet and they tweet frequently. And people want instant response, they want to see tweets instantly and respond to them instantly. I highly doubt you do actually run infrastructure given that you're both misrepresenting what's actually going on here and taking the word of a person who in the article alone shows the various different ways of how he distorts reality. This isn't to say Twitter's infrastructure was great, because all services have heavy amounts of tech debt and cruft associated with years of fixes and updates. But rather that data being sent at high speeds with high reliability and at high frequency leads to high costs.