Difference between Data Transfer and GET request for Amazon S3

Question

I was looking at my billing at noticed my price for Data Transfer made almost 100% of my bill, so I want to be sure I understand exactly what Data Transfer entails, that a GET request. Just for context I host my website on a different server and have it hooked up to an S3 to store user generated files. These files are the made available for download. Does Data Transfer just cover the bandwidth used to download the file, or is it also used to display one of the files store on my s3 on my site. So for example, if I store a mp3 file on my s3, and display this file on the site to play (excluding the downloading), is that just a GET request thats being sent to get and display the file? To me the definitions are little ambiguous. Any help!?

Answer 1

The GET per-request charge is the charge for handling the actual request for the file (checking whether it exists, checking permissions, fetching it from storage, and preparing to return it to the requester), each time it is downloaded.

The data transfer charge is for the actual transfer of the file's contents from S3 to the requester, over the Internet, each time it is downloaded.

If you include a link to a file on your site but the user doesn't download it and the browser doesn't load it to automatically play, or pre-load it, or something like that, S3 would not know anything about that, so you wouldn't be billed. That's also true if you are using pre-signed URLs -- those don't result in any billing unless they're actually used, because they're generated on your server.

If you include an image on a page, and the image is in S3, every time the page is viewed, you're billed for the request and the transfer, unless the browser has cached the image.

If you use CloudFront in front of S3, so that your image or download links point to CloudFront, you would pay only the request charge from S3, not the transfer charge, from S3, because CloudFront would be billing you the transfer charge instead of S3 (and, additionally, a CloudFront per-request charge, but since CloudFront's data transfer charges are slightly cheaper than S3 in some regions, it's not necessarily a bad deal, by any means).