Unbound cache / Timed out DNS cache entries cleaned out?

Hello,
Question regarding Unbound cache handling …
Are timed out cache entires (e.g. www.test.org 300s timeout elapsed) deleted/cleaned from cache at a regular interval?
If not … how does the memory containing timed out cache entries getting re-used?
Tried to find the code in source to get a clue about this but was not successful in locating it.
Thanks for any ‘enlightenment’ :slight_smile:
/pat