Virtually everyone on the Amazon Web Services team has occasion to interact with our developer customers from time to time. This rich source of product feedback gives us a lot of insight into ways that we can do an even better job of meeting their needs as we grow and enhance each of our web services.

Some of the developers building applications with Amazon S3 have been asking us about an SLA, or Service Level Agreement. An SLA defines the minimum acceptable level of performance from a service along with some sort of penalty for not meeting expectations. A typical SLA actually defines a performance or reliability boundary which is somewhat lower than what the system is actually designed, built, and expected to deliver.

We know that many of our customers, including a multitude of teams within Amazon, are using S3 in mission-critical ways and need a formal commitment from us in order to make commitments to their own users and customers.

After talking to many developers to make sure that we fully and precisely understood what the term “SLA” meant to them, we were able to start defining one that was appropriate for S3.

I am very happy to announce that, effective October 1, 2007, The Amazon S3 Service Level Agreement is in effect.

This SLA has been in the works for a while and we take the commitments made in this document quite seriously. We knew that S3 had to meet the very high performance and reliability goals set by our internal clients. We strongly believed that meeting this level of operational excellence would be good enough for our external users as well. Before we published our SLA, we wanted to get a better sense of how our external developers were making use of S3. With well over 5 billion objects under management, we now understand the usage patterns and properties needed to make an informed commitment.

You can read the entire document to see how this will work. Basically, we commit to 99.9% uptime, measured on a monthly basis. If an S3 call fails (by returning a ServiceUnavailable or InternalError result) this counts against the uptime. If the resulting uptime is less than 99%, you can apply for a service credit of 25% of your total S3 charges for the month. If the uptime is 99% but less than 99.9%, you can apply for a service credit of 10% of your S3 charges.

We’re committed to providing a highly available service which meets the needs of current and future customers. This new SLA is our way of formalizing that commitment, letting you know what the minimum expected level of performance will be.

As is the norm with agreements like this, there’s some fine print and you should definitely read it yourself to learn more.

–Jeff;