Both have be implemented with ENTMQBR-3826 but documented just upstream.

https://github.com/apache/activemq-artemis/blob/main/docs/user-manual/en/security.md

The size of the caches are controlled by the authentication-cache-size and authorization-cache-size configuration parameters. Both default to 1000.

How long cache entries are valid is controlled by security-invalidation-interval, which is in milliseconds. Using 0 will disable caching. The default is 10000 ms.