1. A method by a processing system to control recovery of operational state values of a complex event processing (CEP) engine that processes values of events, the method comprising: determining a window size based on a property of an event query; retrieving events' values, from a distributed log, that are restricted to occurring within a timeframe defined based on the window size, wherein the distributed log stores events' values that have been processed by the CEP engine; and replaying the retrieved events' values to the CEP engine for processing to recover the operational state values of the CEP engine.