This benchmark does not, but the fact that Hacker News which is just 70x smaller but conceptually similar runs on a single core on a slow language does. I compl

This benchmark does not, but the fact that Hacker News which is just 70x smaller but conceptually similar runs on a single core on a slow language does. I completely agree that it's probably not be a good idea, but the fact that it's possible or almost possible is still interesting in my opinion. If nothing else the power of modern hardware puts the obsession with horizontal scalability into perspective, since most sites are nowhere near the size of reddit. Even though a pageview on reddit translates to several HTTP requests, only one of those requests has to serve dynamic HTML. The requests that get the JS, CSS and images can go to a content delivery network (and they probably already do). You'd probably indeed want to put the database on the same server, with the vast majority of DB accesses hitting main memory (as you can easily get a server with hundreds of gigabytes or even terabytes of RAM nowadays -- it helps that reddit's access pattern is very heavily concentrated on new posts). Of course you have to replicate to multiple servers to prevent data loss. 9M users and 3,000 servers sounds like a lot. What kind of servers are these? What is the size of the database, roughly?