1. A system for delivering data to a client application over a network, the system comprising: a server in data communication with the network; a client in data communication with the server via the network, a client application executing on the client; a scalable message queuing system in data communication with the server and the client via the network, the scalable message queuing system including a plurality of gateway nodes configured to receive connections from client systems over a network, a plurality of queue nodes containing subscription information about queue subscribers, and a consistent hash table mapping a queue identifier requested on a gateway node to a corresponding queue node for the requested queue identifier; the client being configured to request, for the client application, data associated with an identifier from the server; the server being configured to provide the data associated with the identifier, the data being subject to subsequent change, the server being further configured to establish a queue associated with the identifier at the scalable message queuing system; the client being further configured to subscribe to the queue at the scalable message queuing system to receive invalidation information associated with the data; the server being further configured to signal the queue of an invalidation event associated with the data; the scalable message queuing system being configured to convey information indicative of the invalidation event to the client; and the client being further configured to re-request the data associated with the identifier from the server upon receipt of the information indicative of the invalidation event from the scalable message queuing system.