I don't know what it really looked like but I randomly had 99% of the accounts follow 100 people and 1% follow 5,000. I don't know how many the average account followed but apparently when a single user followed a few thousand it was giving them issues if the user rapidly refreshed the page.

PS: I did not keep old messages just there ID because that was not going to fit in RAM. My assumption was using Redis or other key value store would be fine what they needed was an internal index so you would only need to look up messages that would be displayed.

Note: there current setup once they worked the bugs out handled a peak of over 100,000 tweets per second in 2013. https://blog.twitter.com/2013/new-tweets-per-second-record-a... Which is well beyond the target I was shooting for.