AZ-204 Develop Azure compute solutions Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Enable duplicate detection on the Service Bus queue.

  Why this is correct

  Enabling duplicate detection on an Azure Service Bus queue is the primary mechanism to ensure exactly-once message processing. When activated, Service Bus stores a history of message IDs for a configurable time window, typically up to seven days. If a producer attempts to send a message with an MessageId that matches one already processed within that window, Service Bus automatically rejects the duplicate, preventing its delivery to consumers and thus ensuring that each unique message is processed only once.

• ✗

  Use Peek-Lock mode instead of Receive and Delete.

  Why it's wrong here

  While Peek-Lock mode is crucial for reliable message processing, it does not inherently guarantee exactly-once processing in the context of duplicates. Peek-Lock ensures that a message is not removed from the queue until explicitly completed by the consumer, allowing for retries if the function crashes before completing processing. However, if the function processes the message successfully but crashes before sending the Complete() signal, the message will eventually become available again, potentially leading to duplicate processing if the consumer logic isn't idempotent or if the producer sent the message multiple times.

• ✗

  Set the maxDeliveryCount to 1 on the queue.

  Why it's wrong here

  Setting maxDeliveryCount to 1 on the Service Bus queue dictates that a message will be moved to the dead-letter queue after its first failed delivery attempt. This prevents infinite retries for a problematic message and ensures quick identification of processing failures. However, this setting addresses message retry policy for individual delivery failures, not the prevention of duplicate messages originating from the producer or multiple successful deliveries of the same logical message due to system retries or idempotency issues.

• ✗

  Reduce the batch size in the function host.json.

  Why it's wrong here

  Reducing the batch size in the host.json configuration for an Azure Function's Service Bus trigger controls how many messages are processed concurrently in a single batch by a function instance. This primarily impacts throughput, latency, and resource consumption, potentially reducing the number of messages processed per invocation. However, modifying the batch size has no direct bearing on preventing duplicate messages from being delivered or processed by the function, as it is a scaling parameter, not a deduplication mechanism.