You are designing an Azure Function that will process orders from a new Azure Service...

Enable duplicate detection on the Azure Service Bus queue to suppress duplicate sends. Service Bus tracks application-defined MessageId values during the configured duplicate-detection window. If another message with the same MessageId arrives during that interval, Service Bus accepts the send operation but discards the duplicate message. Microsoft specifically recommends using a deterministic business identifier, such as an order ID, as the basis for MessageId when duplicate suppression is required. Duplicate detection must be enabled when the queue is created and is supported in the Standard and Premium tiers.

For failed or poison messages, implement dead-letter handling . A Service Bus queue has a dead-letter subqueue that retains messages that cannot be successfully processed, including messages that exceed the configured maximum delivery count. Those messages remain available for inspection, troubleshooting, correction, or controlled reprocessing rather than being silently discarded.

Sessions provide ordered/FIFO processing and session affinity; they do not primarily prevent duplicates. An HTTP trigger would bypass the required Service Bus processing architecture.

For strict production-grade exactly-once business effects, the consumer should additionally be idempotent , because a message can still be redelivered after a lock or settlement failure.

Study Guide references: Azure Service Bus → duplicate detection; MessageId; dead-letter queues; poison-message handling; reliable asynchronous processing.