maven-metadata.xml for a group very slow

Question

What are maven-metadata.xml for "groups"? How can we influence whether Maven loads maven-metadata.xml for a group or for a particular repository? And why is loading them for groups so incredibly slow?

/content/groups/public/<groupId-artifactId>/maven-metadata.xml

takes ~22s to load.

/content/repositories/internal-repository-release/<groupId-artifactId>/maven-metadata.xml

takes 32ms.

There was a related bug in Nexus 1.9.2 but we're now on 2.5.1.

Answer 1

Answer I got on the nexus-user mailing list:

"Setting up routing in Nexus properly should help."