There are a few SAS offerings out there that do something similar (https://www.imgix.com/ is another one). The advantage is that they take care of supporting all of the new image types that come out (HEIC/HEIF, etc.) and you can focus on your core business logic. All depends what kind of ‘transformations’ you are doing and if you need the Exif data maintained/updated in the images after modification (I think Imagizer strips the Exif out by default). If you can live with the limitations of these SAS offerings, you may not even need the second app since they’d be doing the hard work…it would essentially just become an asset server.
Another benefit of Cloudfront is that the cache gets copies stored geographically close to the end users, so it improves their page load times, even if your api has only one availability zone.
Without knowing your entire use model, not sure if Broadway, GenStage or even Flow would actually solve your bandwidth problem or not. If the end users expect the image to be served right away, back-pressure on the asset delivery isn’t the greatest solution and you’ll need to build a queuing or retry system in the consuming app to deal with that back-pressure/delay that the Elixir server would be applying. If this is the case, and you actually have a throughput problem, you might look at ways to alleviate the bottleneck before adding a lot of overhead in managing the back-pressure on both sides.
