I have to be honest, I can't remember how much load we tried putting on cloudfront during our testing. We may have just assumed that as cf is a regular cdn and

I have to be honest, I can't remember how much load we tried putting on cloudfront during our testing. We may have just assumed that as cf is a regular cdn and s3 is a big one of a kind data store, s3 was going to be more resilient. We did load test s3 and it scaled linearly (with some caveats). For our use case (a single huge burst of requests) we were willing to drop all caching and pay the additional money. It was absolutely worth it (and under non-sustained load it didn't cost much). We actually used s3 as a sort of cache in front of realtime data. So the client js was accessing objects on s3 that were being refreshed every second. It worked incredibly well where other things (like gae, who disabled our account under load) had failed us in the past.