This is a deprecated feature of Amazon S3 known as Global Endpoints. Some regions support the global endpoint for backward compatibility purposes. AWS recommends that you use the standard endpoint syntax in the future.
For regions that support the global endpoint, your request is redirected to the standard endpoint. By default, Amazon routes global endpoint requests to the us-east-1 region. For buckets that are in supported regions other than us-east-1, Amazon S3 updates the DNS record for future requests (note that DNS updates require 24-48 hours to propagate). Amazon then redirects the request to the correct region using the HTTP 307 Temporary Redirect.
Are there any advantages/disadvantages of excluding the region from the domain? Or are the two domains the same?
- The domains are not the same.
- Advantages to using the legacy global endpoint: the URL is shorter.
- Disadvantages: the request must be redirected and is, therefore, less efficient. Further, if you create a bucket in a region that does not support global endpoints, AWS will return an HTTP 400 Bad Request error response.
TLDR: It is a best practice to use the standard (regional) S3 endpoint syntax.