Reads/sec on a Kinesis shard is capped at 5 and can't be adjusted.

S3 buckets are one I've seen. But there's not really a reason to have 100 s3 buckets, much less more than that.

Yes, that's one that you may not be able to change. From memory, they put that one in place to prevent the equivalent of bucket name squatting (since every bucket has a corresponding public domain name).