How would a "hot" hash key affect throughout in practice on Amazon DynamoDB?

How would a "hot" hash key affect throughout in practice on Amazon DynamoDB?

First, here's a support document for DyanamoDB giving guidance on how to
avoid a "hot" hash key.
Conceptually, a hot hash key is simple and they are (typically)
straightforward to avoid - the documents give good examples of how to do
so. I am not asking what a hot hash key is.
What I do want to know is how much would throughout performance actually
degrade for a given level of provisioned read/write units at the limit,
that is, when all read/write activity is focused on only one (or very few)
partition(s). For properly distributed hash key activity (uniform across
partitions), DynamoDB gives single millisecond response times. So, what
would response times look like in the worst case scenario?
Here's a post on AWS asking a related question which gives a specific
use-case where knowledge of this answer matters.