The world runs on transactional database systems. Every business depends on them, and we each interact with them many times each day. Furthermore the world needs to build thousands more applications of transactional database systems to support the next-generation web. Nothing controversial there, but there is a problem: transactional database systems have stubbornly refused to join the 21st century.
The rest of the world is moving toward data center architectures predicated on thousands of commodity machines, commodity networks, and «scale-out» designs. These data centers will offer on-demand computing services that can instantly increase or decrease capacity to applications as needed. It’s easy to just add more web servers, application servers, or storage servers as required. Unfortunately while that works at every other level in the computing stack it does not work at the database layer. Database systems are scale-up systems, not scale-out systems.