Merge pull request #299885 from jlian/patch-608483

Add maximum message size for each memory profile

Author: prmerger-automator[bot]

articles/iot-operations/manage-mqtt-broker/howto-configure-availability-scale.md

@@ -7,7 +7,7 @@ ms.topic: how-to
 ms.subservice: azure-mqtt-broker
 ms.custom:
   - ignite-2023
-ms.date: 03/17/2025
+ms.date: 05/14/2025
 
 #CustomerIntent: As an operator, I want to understand the settings for the MQTT broker so that I can configure it for high availability and scale.
 ms.service: azure-iot-operations
@@ -174,6 +174,7 @@ When you use this profile:
 
 - Maximum memory usage of each frontend replica is approximately 99 MiB, but the actual maximum memory usage might be higher.
 - Maximum memory usage of each backend replica is approximately 102 MiB multiplied by the number of backend workers, but the actual maximum memory usage might be higher.
+- Maximum message size is 4 MB.
 - The maximum size of the incoming buffer for PUBLISH data is approximately 16 MiB per backend worker. However, the effective size may be lower due to backpressure mechanisms, which activate when the buffer reaches 75% capacity resulting in a buffer size of approximately 12 MiB. Rejected packets have a PUBACK response with a *Quota exceeded* error code.
 
 Recommendations when you use this profile:
@@ -189,12 +190,13 @@ When you use this profile:
 
 - Maximum memory usage of each frontend replica is approximately 387 MiB, but the actual maximum memory usage might be higher.
 - Maximum memory usage of each backend replica is approximately 390 MiB multiplied by the number of backend workers, but the actual maximum memory usage might be higher.
+- Maximum message size is 16 MB.
 - The maximum size of the incoming buffer for PUBLISH data is approximately 64 MiB per backend worker. However, the effective size may be lower due to backpressure mechanisms, which activate when the buffer reaches 75% capacity resulting in a buffer size of approximately 48 MiB. Rejected packets have a PUBACK response with a *Quota exceeded* error code.
 
 Recommendations when you use this profile:
 
 - Only one or two frontends should be used.
-- Clients shouldn't send large packets. You should only send packets smaller than 10 MiB.
+- Clients shouldn't send large packets. You should only send packets smaller than 16 MiB.
 
 ### Medium
 
@@ -213,6 +215,7 @@ Use this profile when you need to handle a large number of client messages.
 
 - Maximum memory usage of each frontend replica is approximately 4.9 GiB, but the actual maximum memory usage might be higher.
 - Maximum memory usage of each backend replica is approximately 5.8 GiB multiplied by the number of backend workers, but the actual maximum memory usage might be higher.
+- Maximum message size is 256 MB.
 - The maximum size of the incoming buffer for PUBLISH data is approximately 2 GiB per backend worker. However, the effective size may be lower due to backpressure mechanisms, which activate when the buffer reaches 75% capacity resulting in a buffer size of approximately 1.5 GiB. Rejected packets have a PUBACK response with a *Quota exceeded* error code.