[bluejade]

At populr.me, we use a variation on the architecture described here. One difference is that we cache resized images to S3, rather than to on-disk cache. This enables all servers to share the cache. Otherwise, when a new server is brought online, it doesn't benefit from the cache, so for a time, every request it receives incurs the most costly path of source image retrieval and resizing.

An added benefit to caching to S3 is that since S3 won't run out of space, we can cache rendered images for longer (we use S3 lifecycle to keep cache expiration simple). The scaled images tend to be smaller than the source images, so the retrieval from S3 is pretty fast. Over the past week, retrieving scaled images from S3 has cost ~46ms versus ~84ms for the larger source images.