http://www.infoq.com/articles/ebay-scalability-best-practices
Best Practice #1: Partition by Function
Best Practice #2: Split Horizontally
Best Practice #3: Avoid Distributed Transactions
Best Practice #4: Decouple Functions Asynchronously
Best Practice #5: Move Processing To Asynchronous Flows
Best Practice #6: Virtualize At All Levels
Best Practice #7: Cache Appropriately