If you need random access to s3 within an ec2 region, sticking nginx in front of it as a caching proxy is unbelievably faster than hitting s3 directly; even moreso if you're multi-region.

I recently experimented with trying to have nginx rewrite images from png/jpeg to webp for clients that support it. I ended up with a solution where a lambda triggered off new files added to a bucket and re-encoded them as webp alongside the originals. When a request came into nginx, it would examine the URL and client Accept headers, and then first try to fetch the webp file from s3 before falling back to fetching the original from s3.

I was somewhat surprised that nginx was capable of doing it efficiently, given the nginx configuration format and all the moving pieces.