I kind of doubt that it's a caching issue. Twitter feels a lot like email to me -- sending a tweet is a lot like emailing to a group of followers. (Though it's unlikely they implement it that way because of the number of tweets that go unread.) Email providers operate at a scale similar to Twitter and don't replace your email with popular emails to increase cache hits.

Maybe to improve profitability you'd want to improve how much you can serve out of memory, but I think Twitter has more than enough compute to just generate your page for you when you visit. (I haven't seen a fail whale for over a decade!)

> sending a tweet is a lot like emailing to a group of followers. (Though it's unlikely they implement it that way because of the number of tweets that go unread.)

My understanding (from a watching a Twitter Tech talk, maybe about redis?) is that that is actually how it is (was) implemented. They were so focussed on time to first render, they took the efficiency hit.

If social networks worked like TV and there were only a few popular channels / pieces of content, sure.

But algorithmic feeds are endlessly unique and composing them is vastly more difficult than doing chronological order.

Isn't each individual person a "channel"?