Actually, unified batch and stream processing in Flink is a bit of false advertisement. In Flink, stream and batch have different API (DataStream vs DataSet) so

Actually, unified batch and stream processing in Flink is a bit of false advertisement. In Flink, stream and batch have different API (DataStream vs DataSet) so reusing logic is not really practical, unless you abstract out everything, in which case you might as well use Spark which is faster than DataSet API. Flink's developers is trying to get rid of DataSet API and move to DataStream and Table API for everything, but it's not done yet.