Status: IN
Message queue delivery guarantees (at-least-once, at-most-once, exactly-once) are enforced entirely at the consumer layer through poll/commit semantics and the two-tier offset mechanism (current vs committed), making the broker stateless with respect to delivery semantics and pushing guarantee selection to the consumer.
The two-tier offset gap (current minus committed) is the mechanism that enables all three delivery modes — the broker just stores offsets, consumers choose semantics
Depends on (SL): dmq-delivery-semantics-in-poll, dmq-two-tier-offset-tracking