Hi @Robert . Ordering should be maintained with RDPs, if you change the number of outgoing connections to 1 per REST Consumer.
Anyhow, I’ve recently been playing with some JCSMP code, testing message ordering and NACKs, so this is timely. Short answer: yes message ordering can change when doing a settle() with an Outcome of FAILED . The only way it cannot is if you set the queue’s “max unacked messages per flow” to 1. Otherwise, there will be other messages pulled down off the queue, and when you NACK one message, the next one will be given to the client application before the NACK goes up to the broker and the message resent back down to the consumer.