Ehh, first off the 2009 twitter was vary different than the 2014 beast. For some context: http://computer.howstuffworks.com/internet/social-networking...

Back when they where growing from 500,000 users to 7 million total users they where having major issues and that's when I was looking into things.

Anyway, not I was suggesting 1GB would be fine today. Still, I was saturating a 1GB connection so 15M (over twice the total users back then) * ~200bytes * 8 / ~1000^3 = ~24 seconds did you have an extra 60x multiplier in there somewhere?