There is disclosed a method, apparatus and computer program for an application instance to request attachment to a queue partition on a messaging server within a plurality of messaging servers, each messaging server holding at least one queue partition, the set of queue partitions together forming a single queue. An application instance requests attachment to a queue partition, the request requesting exclusivity with regard to other application instances having a common identifier. Responsive to an indicating that the request has been successful, the application instance interacts with the queue partition.