Techniques are described for processing data. Embodiments receive streaming data to be processed by a plurality of processing elements. An operator graph of the plurality of processing elements that defines at least one execution path is established. Additionally, a first processing element in the operator graph includes a barrier operator that joins the output of one or more upstream operators included in one or more of the plurality of processing elements. Embodiments initiate one or more timeout conditions at the barrier operator. Embodiments also determine, at the first processing element, that one or more timeout conditions have been satisfied before data has been received from each of the one or more upstream operators. Upon determining that the one or more timeout conditions have been satisfied, embodiments generate output data at the barrier operator without the data from at least one of the one or more upstream operators.