In a recent blog post on the Trello Stack, Brett Kiefer wrote:
MongoDB fills our more traditional database needs. We knew we wanted Trello to be blisteringly fast. One of the coolest and most performance-obsessed teams we know is our next-door neighbor and sister company StackExchange. Talking to their dev lead David at lunch one day, I learned that even though they use SQL Server for data storage, they actually primarily store a lot of their data in a denormalized format for performance, and normalize only when they need to.
Could David (or anyone else from the team) give some more info on exactly how you "primarily store a lot of data in a denormalized format"? The implication (from the phrasing on the Trello blog, at least) is that you store the denormalized data in a non-MSSQL database. Is this done in Redis (the use of which on SE is already documented)? Something else (MongoDB)? How far do you go with denormalization and what gains have you seen from this?