Advantages of the SimpleDB model
SimpleDB's alternative approach for storing data can be advantageous for meeting your application needs when compared to a traditional relational database. Here's the list of advantages:
Reduced maintenance as compared to a relational database
Automated indexing of your data for fast performance
Flexibility to modify or change your stored data without the need to worry about schemas
Failover for your data automatically being provided by Amazon
Replication for your data across multiple nodes also handled for you by Amazon
Ability to easily scale up in response to increased demand without worrying about running out of hardware or processing capacity
Simplified data storage and querying using a simple API
The lack of object-to-relational mapping that is common for an RDBMS allows your structured data to map more directly to your underlying application code and reduce the application development time