Seen recently while profiling dx-core 6.2.14-SNAPSHOT (as configured out of the box) under heavy load with
$ wrk -c200 -t200 -d600s --timeout 20s --latency --header "User-Agent: wrk" http://localhost:8080/magnoliaPublic/travel.htm.

Decoration involves checking for a resource's last modified date/time. This causes multiple threads to try and log to JR via its user manager and wait (JR's user manager uses a single synchronised session to manage log in credentials, see org.apache.jackrabbit.core.security.user.UserManagerImpl#session).

Possibly mitigate the issue by checking last modified every n seconds instead of each request? 

(If you're wondering who's triggering the topmost result (16.8% - ~23s), that's PersonalizedCachePolicy#shouldCache)