Service Oriented Architectures are increasingly popular but there are not many "best practices" architectures that define the data access and caching needs for building large scale SOA systems. This white paper details best practices for building SOA applications that support thousands of users and hundreds of transactions per second with guaranteed availability. It uses real-world examples to demonstrate the advantages of implementing "shared data services" architectures to deliver on the true promise of SOA-rapid application development through reusable components with fast, accurate, reliable, and resilient shared enterprise data access.