Systems and methods are described for processing queue data and for providing queue messaging over a network. An illustrative queuing system includes a first queue configured to hold resource requests from a plurality of users, and program code stored in computer readable memory configured to determine or estimate whether a resource requested by a first resource request submitted by a first requester will be available when the first resource request will be serviced, and to transmit a message over a network to the first requester indicating that the requested resource will not be available when the queued request is serviced if it is estimated or determined that the requested resource will not be available when the first request is serviced.