Efficient sorting for a stream processing engine

The techniques and systems described herein are directed to incremental sorting in a stream processing engine. For example, because of network delays, streaming data can be received at a stream processing engine that is out-of-order with respect to the timestamp of the event generation. Streaming data can be incrementally sorted by partitioning events into ordered runs, which provide intermediate arrays of ordered elements. Upon an assertion of a punctuation event (e.g., a progress indicator), partial runs can be output and merged to form sorted streaming data. Further, the sorted streaming data can be used to provide speculative outputs based on speculation latencies, which improves throughput and completeness of processing on the streaming data.