We don't really cache that much, for example: every post, comment, user, etc. on the page is pulled and rendered live. We output cache certain pages for 60 seconds for anonymous users, but it has almost no performance impact (I think it's a 4% hit rate?)
Some things are cached, but each page render is very dynamic - more so than most I think? I don't have a great source of comparison for similar sites though.
Nick, first of all great write-up, it's really nice when people take time from their schedule to write such detailed informations about how their internal systems work!
I could be wrong but from the article and the numbers you posted it seems that you do cache 89% of your db queries results so maybe this is what jldugger referred to :
504,816,843 (+170,244,740) SQL Queries (from HTTP requests alone)
5,831,683,114 (+5,418,818,063) Redis hits
Ah I see the confusion now. To clarify: we use redis for a great many things, not just serving HTTP requests. For example, we use redis lists and sets to continually recalculate mobile feeds for users - that's roughly 4 billion of the hits every day.
