Amazon has been offering its customers computing infrastructure via Amazon Web Services (AWS) since 2006. AWS aims to use its own infrastructure to provide the building blocks for other organizations to use. The Elastic Compute Cloud (EC2) is an AWS offering that enables you to spin up virtual servers as you need the computing power and shut them off when you are done. Amazon Simple Storage Service (S3) provides fast and unlimited file storage for the web. Amazon SimpleDB is a service designed to complement EC2 and S3, but the concept is not as easy to grasp as “extra servers” and “extra storage.” This chapter will cover the concepts behind SimpleDB and discuss how it compares to other services.