Eric Heuveneers has written "Introduction to Amazon S3" for OnJava, showing how to access Amazon's "Simple Store Service" from a fairly low level. What is Amazon S3?

Amazon S3 provides a simple web services interface that can be used to store and retrieve any amount of data, at any time, from anywhere on the web. It gives any developer access to the same highly scalable, reliable, fast, inexpensive data storage infrastructure that Amazon uses to run its own global network of web sites. The service aims to maximize benefits of scale and to pass those benefits on to developers.

There are APIs to access S3 from Ruby, Python, the bash shell, C#, PHP, and - of course - Java, including Amazon's Java S3 toolkit, JetS3t, and even an OSCache plugin that uses S3. Even with libraries that provide access to S3, though, understanding what the underlying protocol is and how it can be used is always useful.

Amazon S3 should support some sort of locking. There was a rumor somewhere that creating a bucket is an atomic operation (i.e. if I fail to create one since one already exists, then I can implement simple locking on top of it), but it turns out that this is not the case.

Lets imagine you can do everything with Amazon S3. But what would you use it for? What application to write with it? I am looking for applications for it outside of the Amazon software development team. Does anyone have an idea?

One useful case is using S3 as persistence backend for lightweight business applications developed with RIA or RDA technologies, like Flex, Open Laszlo. I think Amazon S3 can really open the field here.

this is an interesting example of what you can do with Amazon S3 + EC2 + java: Self-service, Prorated Super Computing Fun!