Since RichFaces4 strongly supports GAE I propose to discuss ability to utilize Google channel API http://code.google.com/intl/en/appengine/docs/java/channel/overview.html. Scenarios could be different. For example don’t use render attribute, instead make decision what to rerender in server side, after send message to client. Client render part of a page on the basis of message from server. It could be very interesting approach with weld event driven model.