[morsch]

No. I've introduced state, but no shared state; the "next batch" var is local to the actor and not shared.

Critically, the only one who updates the variable is the actor itself in its thread; it could be a plain list, and not a concurrent queue as it might be in a different multiple producer/single consumer architecture.

PS -- I'll add that in Akka itself, the actor's mailbox, in which messages accumulate until the actor next gets allotted a thread, is exactly a kind of concurrent queue, at least in its default implementation.