Systems and methods according to embodiments provide elasticity for complex event processing (CEP) systems. Embodiments may comprise at least the following three components: (1) incremental query optimization, (2) operator placement, and (3) cost explanation. Incremental query optimization allows avoiding simultaneous computation of identical results by performing operator-level query reuse and subsumption. Using automatic operator placement, a centralized CEP engine can be transformed into a distributed one by dynamically distributing and adjusting the execution according to unpredictable changes in data and query load. Cost explanation functionality can provide end users with near real-time insight into the monetary cost of the whole system, down to operator level granularity. Combination of these components allows a CEP system to be scaled up and down.