Please do not comment without reading the article. You do not even have the word SQL in it. Sergei is addressing the different approaches to achieve Consistency

Please do not comment without reading the article. You do not even have the word SQL in it. Sergei is addressing the different approaches to achieve Consistency/Availability and Performance between their solution and MongoDB. A good read and I must say, I would really love to have more details and more general overview of their algorithms. They could be used for other problems. Note that I am a huge fan of MongoDB and using it in production since the 1.4 something release.