If you are using S3 as a CDN, you will need to give WordPressW3TC plugin access to your AWS account so it can upload files to S3 on behalf of you. The smart way to do this is to create a new AWS user who can only access what they need for W3TC to do its job. Who wants to store the keys to their whole AWS account in their WordPress based site? If that information is retrieved by a hacker, they could do tons of damage. If they only gain access to your site’s specific bucket, there is less damage to be done.

If you have ever used Amazon’s AWS console then you probably know that though sometimes it can be clunky, it has a ton of functionality for interacting with the various AWS services. So when I needed to give one of my coworkers access to one of our S3 buckets, I immediately investigated the laziest option: Figuring out how they could login to the S3 console and use that to manage the bucket.