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When MQTT client connects, it locally create JMS-like consumer to the broker. By default In older versions this consumer is was created with the prefetch size of 1 (message prefetching is explained here in more details). Usually, increasing message prefetch size can boost the performance as messages are dispatched to consumers in batches instead of waiting for the individual acknowledges. To increase Starting with 5.11.0 release, the prefetch size is adjusted to the default value for the appropriate JMS subscription. QoS=0 subscriptions have default prefetch of regular non-persistent topic subscriptions, while QoS=1 and QoS=2 are assigned prefetch size of durable subscribers or the queue subscriptions depending on the subscription strategy used (see the next section for more details). Default prefetch values are listed here.
To change default value of the prefetch size, you can use activeMQSubscriptionPrefetch transport option, like
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