Great paper. I tend to work on medium scale systems but I always enjoy reading material from companies like Google, Facebook and Twitter on how they manage scaling, especially data stores.

There is an interesting pattern: the more scalable a data store is the larger the hassle of writing application code against it. I am lucky that MongoDB master slave has been sufficient for what I have been doing because it is almost as simple to use as a RDMS. It is clear that writing against HBase and Cassandra takes more effort and it is more difficult to be in an agile development mode.