Some async engine processors use List#get() method in a cycle iterating over all the records, sometimes several times, e.g. iterating also over created Future objects.
It seems that calling this method is very slow and causes huge slowness of these processors, see attached picture from async profiler, showing that about 99.5% of time is spent in List#get(). Using List.stream() or iterating over the record via iterator is much faster and should be used in all these processors instead of calling List#get().