Tumblr Architecture - 15B Page Views a Month and Harder to Scale than Twitter
Always interesting to read about real-world usage of different tools and languages.From the article: 
...
•  MySQL (plus sharding) scales, apps don't. 
•  Redis is amazing. 
•  Scala apps perform fantastically.
...Some of the organizations (Including Tumblr) using Scala were discussed as part of this talk:
http://www.youtube.com/watch?v=qqQNqIy5LdM
and slides here:
http://mrkn.co/s/video_martin_odersky_what_s_next_for_scala,...