Generally speaking this isn't something Amazon S3 customers need to worry about - as others have said, S3 will automatically scale index performance over time based on load. The challenge primarily comes when customers need large bursts of requests within a namespace that hasn't had a chance to scale - that's when balancing your workload over randomized prefixes is helpful.
Please see the documentation: https://docs.aws.amazon.com/AmazonS3/latest/userguide/optimi...
This 2024 re:Invent session "Optimizing storage performance with Amazon S3 (STG328)" which goes very deep on the subject: https://www.youtube.com/watch?v=2DSVjJTRsz8
And this blog that discusses Iceberg's new base-2 hash file layout which helps optimize request scaling performance of large-scale Iceberg workloads running on S3: https://aws.amazon.com/blogs/storage/how-amazon-ads-uses-ice...