Twitt Er uses Ruby On Rails.
Alex Payne complained about Scalabil Ity problems, esp associated with Rails supporting connection to only a single Data Base.
DHH [[http://www.loudthinking.com/arc/000608.html |replies]]
then points to a sudden patch by Nic Williams to support multi dbs. In the comments, Blaine Cook provides more details of the actual Twitt Er situation: For the record, Twitter is not currently database bound, and won't be for at least a month (unless our growth rate increases), something that David was aware of when we spoke to him a couple of weeks ago... The current largest bottleneck we have without a clear solution (other than hand-optimization) is the cost of rendering templates (Template System)... I hope that my talk on Sunday at SDForum will clarify our experience with Rails at Twitter, and offer insights to others. Here's Blaine's own blog post.
Another perspective on talking to multiple databases.
Jens Alfke wonders whether a Data Base is even needed, vs just using the File System.