1. A system including instructions recorded on a computer-readable medium, the system comprising: a query pattern handler configured to determine at least one query pattern to be matched against a stream of events, and configured to determine a plurality of run-time patterns representing active instances of the at least one query pattern which are currently available for matching, and which are expressed as finite state machines including a plurality of states; an event scheduler configured to receive an event of the stream of events, the event associated with a current event set of the stream of events; a run-time pattern scheduler configured to determine, at runtime, a ranked set of the run-time patterns based on a priority metric which includes, for each run-time pattern, an expectation of completion that is determined based on a length of each independent path through each state machine and a probability of completion of each path; and a pattern match evaluator configured to evaluate each run-time pattern of the ranked set, in turn, against the current event set.