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Backend question · Message queues & streaming › RabbitMQ: acks, prefetch & dead-lettering

Which statement about RabbitMQ 4.x quorum queues is correct?

They replicate with Raft, need a majority of replicas to accept writes, and enforce a delivery limit (20 by default since 4.0) after which a message is dropped or dead-lettered

Quorum queues replicate with Raft and need a majority of replicas to accept writes. Raft is a consensus algorithm: it lets several servers agree on the same data. A quorum queue stays available while a majority of its replicas is up.

"They are classic mirrored queues renamed, and still use mirroring policies" is wrong. RabbitMQ 4.0 removed classic mirrored queues, and quorum queues replace them.

"They allow unlimited redeliveries" is also wrong. Since 4.0, quorum queues have a default delivery limit of 20. This stops endless requeue loops.