Before, we were using the ContentType from the S3 object, which was unreliable. This helps us behave better for query-string files!
We also add a filename via Content-Disposition for the files that auto-download and for the Save As case. Idk if this is super important exactly, but I feel like it'll be a lifesaver for anyone using this to get at a specific file for their own reference at any point! and it just seems polite lol