Caching, uniqueness and security

The documentation for caching notes that we can specify the cache keys.

What is used as the default cache key? Is it a hash of the request template?

The announcement blog post shows an example using the user sub as an additional cache key to "ensure the uniqueness of the cached value". How in this example would not using the sub impact the uniqueness?

What security considerations are needed based on the answers to the above?

Start with the caching documentation and the announcement blog post referenced in the issue. Verify the default cache-key behavior, how adding the user sub affects uniqueness, and the resulting security considerations. The documentation update is done when these questions are answered clearly and consistently.

Written by the indexing model from the issue text.