Flow router verify URL

A simple example: /subject/:id/discussion

FlowRouter clearly encourage template/layout level authorizations and permissions, how would I then make sure the :id parameter actually exists (ie, id would be subject’s id) If there’s /subject/:id/discussion, do I have to subscribe to ALL subjects and do a Subjects.findOne({_id: id}) in onCreated to make sure id is valid ? (it seems wasteful since I do not require subject subscriptions at all) I’m sure there’s a better way out there