Merge pull request #310306 from dominicbetts/central-note

IoT Central: File upload throttling notes

Author: prmerger-automator[bot]

articles/iot-central/core/concepts-architecture.md

@@ -106,6 +106,9 @@ IoT Central applications internally use multiple Azure services such as IoT Hub
 
 IoT Central automatically scales its IoT hubs based on the load profiles in your application. IoT Central can scale up individual IoT hubs and scale out the number of IoT hubs in an application. IoT Central also automatically scales other underlying services.
 
+> [!NOTE]
+> IoT Central's auto scale behavior doesn't consider **file-upload operations**. If your solution relies heavily on file uploads, you may need to manually scale the underlying IoT Hub instance to avoid throttling. If this is the case, contact Microsoft support.
+
 ### Data export
 
 IoT Central applications often use other, user configured services. For example, you can configure your IoT Central application to continuously export data to services such as Azure Event Hubs and Azure Blob Storage.

articles/iot-central/core/howto-configure-file-uploads.md

@@ -19,6 +19,9 @@ You can also manage and preview files uploaded by your devices inside your IoT C
 
 To learn how to configure file uploads by using the IoT Central REST API, see [Add a file upload storage account configuration](howto-manage-iot-central-with-rest-api.md#add-a-file-upload-storage-account-configuration).
 
+> [!NOTE]
+> IoT Central's auto scale behavior doesn't consider **file-upload operations**. If your solution relies heavily on file uploads, you may need to manually scale the underlying IoT Hub instance to avoid throttling. If this is the case, contact Microsoft support.
+
 ## Prerequisites
 
 You need to be an administrator in your IoT Central application to configure file uploads.
@@ -43,6 +46,16 @@ To configure device file uploads:
 
 :::image type="content" source="media/howto-configure-file-uploads/file-upload-configuration.png" alt-text="Screenshot that shows a properly configured file upload." lightbox="media/howto-configure-file-uploads/file-upload-configuration.png":::
 
+## Best practices to avoid unexpected throttling for file upload scenarios
+
+To avoid unexpected throttling when using file uploads, consider the following best practices:
+
+- Stagger uploads across devices.
+- Avoid synchronized uploads. For example, at top of the hour.
+- Implement client-side exponential backoff on `429 / ThrottleBacklogTimeout` errors.
+- Consider alternative ingestion mechanisms such as ADX ingestion, Fabric pipelines, or direct storage writes.
+- Test workload behavior under expected production upload patterns.
+
 ## Disable device file uploads
 
 To turn off device file uploads in your IoT Central application: