In The Cloud at Your Service, published in 2011, sharding is deemed to be the preeminent way to design for scale. Although sharding continues to be the preeminent architectural pattern, elastic transactional databases for the cloud, using open source databases, such as MySQL or PostgreSQL, is the future.
Elastic MySQL Dot Com, or alternatively, and more academically put, the use of elastic, open-source, scalable, and self managing transactional databases for the cloud, has been and is a hot topic in academia. A fairly recent paper by Das et. al. stops short of addressing what the major cloud service providers would need to do to provide Elastic MySQL Dot Com, most likely because thats where the real money lies. That said, the cited paper is, in effect, the writing on the wall when it comes to the future of how the elaphant in the room (the problem of dealing with transactional data stores at scale) will be addressed.
As an aside, I’m writing a white paper on this topic, but there is a fair chance it may stay in perpetual draft format. Rest assured however that the research labs of the major cloud service providers are humming when it comes the Elastic MySQL Dot Com – just look at who sponsored the ElasTraS research. One could only hope that some of the work will be in the public domain, and patent free, ala Eucalyptus.