How has the scaling effort gone? In the first post you mentioned that you were just rewriting code to remove bottlenecks. Have you had to make any more exotic and interesting changes to the code base since then to support the growth?
Point of comparison, as of March 2011 Stack Overflow, which got about 2x the traffic for page hits/month, used 12 cores for the web tier and 12-24 cores for their SQL Server 2008 database(s?). Source - http://highscalability.com/blog/2011/3/3/stack-overflow-arch...
Does anyone know what db engine serves as backend for HN?
A Stack Overflow page I'd imagine would be so much more complex than a Hacker News page to render. Would likely require lots of complex queries for everything going on around the primary question and answer mechanism. By contrast Hacker News seems fairly simple.
These are the results of different constraints. SO wants a slick, interactive interface with a lot of access to long-tail content. HN wants inexpensive and easy-to-maintain that still allows discussion of active topics that fade from view fairly quickly.
