A side note. We were talking about `take(n).take(d)` vs. `take(d).take(n)` and they are equivalent, and therefore no need for take(n, d).

groupedWithin is different. groupedWithin will emit the group immediately after n elements or d duration, whatever happens first. A more flexible groupedWithin is suggested in bunch: https://github.com/akka/akka/issues/15237