Yes I'm aware that Flink has these mechanisms. But I'm not sure I understand how Differential Dataflow handles this in a better way. For simple windowing funct

Yes I'm aware that Flink has these mechanisms. But I'm not sure I understand how Differential Dataflow handles this in a better way. For simple windowing functions there are certainly shortcuts possible, but for more complex ones such as session windows it gets complicated. You might have to merge sessions as late data arrives. This is what Flink and others (Google Dataflow) do.