I'd like to set up an Thumbor to transform images and then put cloudfront on top of it with a custom subdomain

So it would be thumborapp.up.railway.app > dxxxx.cloudfront.net > img.site.com

Is it a simple case of creating a new distribution and setting the thumborapp.up.railway.app URL as the origin? I'm not using S3 to store original files (only to keep copies of the transformations). So Thumbor will refer to my origin host for new transformations, and will redirect traffic to S3 for already generated images once the edge does not have the file in storage.

When I tried to reference the transformed URL with Cloudfront (i.e. https://dxxxx.cloudfront.net/xxx/image.jpg), I got a 404. I know it's hitting Railway but I'm not sure why it's giving a 404 yet the image transform and displays correctly if I do it via the original Railway URL

HTTP/1.1 404 Not Found Content-Type: application/json Content-Length: 101 Connection: keep-alive Server: railway-edge X-Railway-Edge: railway/us-east4-eqdc4a X-Railway-Fallback: true X-Railway-Request-Id: Rlhc9CNUQo-YCdB3woOzXw Date: Fri, 12 Dec 2025 20:45:56 GMT X-Cache: Error from cloudfront Via: 1.1 50adcd6749b8cd1a89ce54c8bb0b335a.cloudfront.net (CloudFront) X-Amz-Cf-Pop: MIA50-P2 X-Amz-Cf-Id: bl5d8wYr31gVykGa6flgdWOi-UYzS-RDzfOLE2NBiDMcyy1eOfIJyQ==