"This S3 request rate performance increase removes any previous guidance to randomize object prefixes to achieve faster performance. That means you can now use logical or sequential naming patterns in S3 object naming without any performance implications."
https://aws.amazon.com/about-aws/whats-new/2018/07/amazon-s3...
1) The performance per partition increased
2) The way AWS created partitions changed
When I was at Mozilla, one thing I worked on was Firefox's crash reporting system. It's S3 storage backend wrote raw crash data with the key in the format `{prefix}/v2/{name_of_thing}/{entropy}/{date}/{id}`. If I remember correctly, we considered this a limitation since the entropy was so far down in the key. However, when we talked to AWS Support they told us their was no longer a need to have the entropy early on; effectively S3 would "figure it out" and partition as needed.
EDIT: https://news.ycombinator.com/item?id=30373375 is a good related comment.