An embodiment of the invention provides a method for exploiting stateless and stateful data parallelism in a streaming application, wherein a compiler determines whether an operator of the streaming application is safe to parallelize based on a definition of the operator and an instance of the definition. The operator is not safe to parallelize when the operator has selectivity greater than 1, wherein the selectivity is the number of output tuples generated for each input tuple. Parallel regions are formed within the streaming application with the compiler when the operator is safe to parallelize. Synchronization strategies for the parallel regions are determined with the compiler, wherein the synchronization strategies are determined based on the definition of the operator and the instance of the definition. The synchronization strategies of the parallel regions are enforced with a runtime system.