t "aggregate" is
> > connected to, and read / check if the corresponding entry is already
> > `success`, if yes let `transformValue` to return `null` which means
> forward
> > nothing to the downstream.
> >
> > The reason to use transformValues instead of t
So I am trying to process incoming events, that may or may not actually
update the state of my output object. Originally I was doing this with a
KStream/KTable join, until I saw the discussion about "KTable in Compact
Topic takes too long to be updated", when I switched to
groupByKey().aggregate().
