The develop branch was modified to use pre-signed URLs rather than the Authorization header. With this format, I'm unable to authenticate with DynamoDB (I've actually only tried DynamoDB Local):

Request must contain either a valid (registered) AWS access key ID or X.509 certificate.

I checked AdRoll/goamz and the JS SDK, and both use the Authentication header rather than pre-signed URLs with DynamoDB. In particular, goamz only generates pre-signed URLs when the X-Amz-Expires header is set, and only the S3 signer leverages this.

My understanding of AWS auth is limited, but it seems that the pre-signing logic should only apply to S3, and other services should revert to using the Authentication header.