I am working on VersionEye.com and in the last days we had some performance issues. I added some new data to the database and to the views. The rendering of the package detail pages tooked sometimes up to 5 seconds. And because the UI is programmed with Ruby on Rails, some people told me: “Yes of course, Ruby is slow, you should use Java!”.
Hell, No! That was not the problem. I just added some indexes to the database, so that they fit perfectly to the queries. And now, it is crazy fast 🙂 Some pages get rendered in less than 80 milli seconds 🙂