This 2024 re:Invent session says exactly the opposite:

"If you want to partition your data even better, you can introduce some randomness in your key names": https://youtu.be/2DSVjJTRsz8?t=2206

FWIW The optimal way we were told was to partition our data was to do this: 010111/some/file.jpg.

Where `010111/` is a random binary string which will please both the automatic partitioning (503s => partition) and manual partitioning you could ask AWS. Please as in the cardinality of partitions grows slower at each characters vs prefixes like `az9trm/`.

We were told that the later version makes manual partitioning a challenge because as soon as you reach two characters you've already created 36x36 partitions (1,296).

The issue with that: your keys are no more meaningful if you're relying on S3 to have "folders" by tenants for example (customer1/..).