Amazon Simple Workflow Service
Developer Guide (API Version 2012-01-25)

Amazon Simple Workflow Service Endpoints

A list of the current Amazon SWF Regions and Endpoints are provided in the Amazon Web Services General Reference, along with the endpoints for other services.

Amazon SWF domains and all related workflows and activities must exist within the same region to communicate with each other. Furthermore, any registered domains, workflows and activities within a region don't exist in other regions. For example, if you create a domain named "MySampleDomain" in both us-east-1 and in us-west-2, they exist as separate domains: none of the workflows, task lists, activities, or data associated with your domains are shared across regions.

If you use other AWS resources in your workflows, such as Amazon EC2 instances, these must also exist in the same region as your Amazon SWF resources. The only exceptions to this are services that span regions, such as Amazon S3 and IAM. You can access these services from workflows that exist in any region that supports them.