Amazon.com will soon begin a limited-release test of an upcoming Web-based database that will work closely with its S3 online storage service and EC2 online application hosting service.

The database, called SimpleDB, is aimed at application developers looking for a less expensive, easier-to-use alternative to a full relational database, primarily for running real-time queries against structured data.

SimpleDB "provides the core functionality of a database -- real-time lookup and simple querying of structured data -- without the operational complexity," according to information posted on Amazon.com's Web site. The database service will automatically index data and do performance tuning, allowing Web developers to work without the aid of a full-time database administrator, the company said.

Users interested in participating in the limited beta, which is scheduled to start in several weeks, can sign up on the Amazon.com site, although doing so requires that you either have an existing Amazon account or create one.

Despite being best known as an online retailer, Amazon.com's moves into cloud-based computing -- an arena that Microsoft, IBM and other IT vendors also want to dominate -- have been hailed by some users, especially those involved in Web 2.0 computing.

The cost of the company's services is one of the benefits that have been cited. For instance, S3 lets users store 1GB of data for just 15 cents per month.

Storing data in structured form in SimpleDB, instead of the raw storage that S3 offers, will cost US$1.50 per gigabyte monthly, according to Amazon.com. In addition, the company said that database requests will cost 14 cents for each machine hour of processing time used, based on the hourly capacity of a "circa 2007" 1.7-GHz Xeon processor. The cost of transferring data into SimpleDB will be 10 cents per gigabyte, while outward data transfers will start at US$0.18 per gigabyte for the first 10TB of information transferred in a given month.

SimpleDB is designed to store relatively small amounts of information and then to provide fast access to the data, Amazon.com noted. To keep storage costs down, it recommends that users store large objects and files in S3 and put pointers and metadata associated with the files in SimpleDB.

The Amazon.com technology isn't the first "Database 2.0" service to hit the market. Trackvia formally launched its online database in August, and the IT Redux Web site lists 13 others including Google's Google Base and Intuit's QuickBase.

Developers who want more features than a Web-based database provides can use MySQL AB's namesake open-source software and store data in Amazon.com's S3 service via a third-party plug-in.

Users also can connect data stored in S3 to database applications hosted in EC2. S3 is shorthand for Simple Storage Service, while EC2 stands for Elastic Compute Cloud.