why not just a "findByID" ? 

The ```instanceId``` is the PK, right ? So that is already supported by the generic DAO:
https://github.com/aerogear/aerogear-unified-push-server/blob/master/src/main/java/org/jboss/aerogear/connectivity/jpa/AbstractGenericDao.java#L56-L58

I guess it's just a matter of exposing to the service layer