I'm trying to figure out if I can get browsers to cache images with signed urls.

What I want is to generate a new signed url for every request (same image, but with an updated signature), but have the browser not re-download it every time.

So, assuming the cache-related headers are set correctly, and all of the URL is the same except for the query string, is there any way to make the browser cache it?

The urls would look something like:

http://example.s3.amazonaws.com/magic.jpg?WSAccessKeyId=stuff&Signature=stuff&Expires=1276297463
http://example.s3.amazonaws.com/magic.jpg?WSAccessKeyId=stuff&Signature=stuff&Expires=1276297500

We plan to set the e-tags to be an md5sum, so will it at least figure out it's the same image at that point?

My other option is to keep track of when last gave out a url, then start giving out new ones slightly before the old ones expire, but I'd prefer not to deal with session info.