Amazon SimpleDB passes on to you the financial benefits of Amazon’s scale. You pay only for resources you actually consume. For Amazon SimpleDB, this means data store reads and writes are charged by compute resources consumed by each operation, and you aren’t billed for compute resources when you aren’t actively using them (i.e. making requests).

While SimpleDB has scaling limitations, it may be a good fit for smaller workloads that require query flexibility. Amazon SimpleDB automatically indexes all item attributes and thus supports query flexibility at the cost of performance and scale.