, a Web service providing core database functions such as indexing and querying, will be free for at least the next six months under the public beta that started Monday, the company said. The service had been in private beta testing for about a year.

"For at least the next six months, you can consume up to 500 MB of storage, and you can use up to 25 machine hours each month. You can transfer 1 GB of data in, and another 1 GB out. You can move as much data to and from Amazon EC2 as you would like, for free," AWS said in a .

The company isn't saying yet if the service will continue to be free after the six months is up, however.

AWS also reduced the price for structured data storage through the service. The price has been cut to US$0.25 per G byte per month, from $1.50 per G byte per month.

Amazon SimpleDB is one of AWS's Web-based "cloud computing" infrastructure services that companies can use to build and host applications. It also offers the Elastic Compute Cloud (EC2), Simple Storage Service (Amazon S3), Simple Queue Service (Amazon SQS), Flexible Payments Service (Amazon FPS) and the recently released CloudFront.