As the scale of web applications is expanding, an increasing number of websites are breaking away from the mould of SQL-based databases and adopting something different. Amazon till now has been offering a database called SimpleDB for such people, but now they have a new offering, called DynamoDB.
DynamoDB is based on Amazon engineers's own experiences with developing non-relational database based websites that needed to be scaled. It also aims to improve over their older NoSQL service SimpleDB in terms of "domain scaling limitations", "predictability of performance" and "pricing complexity."
Taking the best of their original Dynamo design from nearly 5 years back, and their SimpleDB NoSQL database, they have come up with DynamoDB, which is a fully managed non-relational database service that Amazon will now offer.
DynamoDB can scale endlessly, spreading data to hundreds or even thousands of servers. The data is replicated across three different data centers, and for best performance their databases are stored on SSD drives.
Currently the service is in beta and offers a free tier of 100MB storage, 5 writes / second, and 10 reads / second. For more information, you can read this detailed blog post by Werber Vigeks, the CTO of Amazon.com, describing DynamoDB and its evolution.