Druid is an in-memory high-speed analytic database that is distributed in a cloud platform. MetaMarkets says they plan to release the code in the coming year. Data is fed in a semi-aggregated form from a Hadoop backend that stores the raw data. Their cluster of 40 modest machines churns through 1 billion rows of arbitrary dimensionality in 1 second. In another post they mention that they can use 6TB of memory spread among multiple machines before they incur degradation in speed due to cloud communication overhead.