DVA-C02 Development with AWS Services Practice Question

A developer wants exactly-once processing semantics for commands submitted to a queue where duplicate command IDs must be rejected within five minutes. Which SQS feature is most directly relevant?

⚠ Common exam trap

Many exam-takers confuse visibility timeout (which controls reprocessing) with deduplication (which prevents duplicate submissions), leading them to select option D instead of the correct FIFO deduplication ID feature.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

FIFO queue deduplication ID

FIFO queues support exactly-once processing by using a deduplication ID. When a message with a given deduplication ID is sent, SQS automatically rejects any duplicate within a 5-minute deduplication interval. This directly meets the requirement to reject duplicate command IDs within five minutes.

Answer analysis

Option-by-option breakdown

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

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Standard queue delay seconds
Why it's wrong here
Standard queue delay seconds merely postpones when a message becomes available for consumption, typically used to give producers time to complete related tasks before a message is processed. It offers no inherent mechanism to prevent duplicate messages from being sent to the queue or to ensure that a message is processed only once if a consumer fails and the message reappears, thus failing to meet exactly-once processing requirements.
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Dead-letter queue redrive policy
Why it's wrong here
A dead-letter queue (DLQ) redrive policy is designed to capture messages that fail to be processed successfully after a specified number of retries, preventing them from blocking the main queue. While crucial for robust error handling and preventing message loss, it does not prevent duplicate messages from being initially sent to the queue or guarantee that a command is processed exactly once if a consumer successfully processes it but then fails to delete it before the visibility timeout expires.
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FIFO queue deduplication ID
Why this is correct
The "MessageDeduplicationId" in an Amazon SQS FIFO queue is the primary mechanism for achieving exactly-once processing semantics by preventing duplicate messages from being added to the queue. When a producer sends a message with a specific deduplication ID, SQS ensures that any subsequent message sent with the same ID within a 5-minute deduplication interval is treated as a duplicate and not delivered to the queue. This directly guarantees that a command is enqueued and thus processed only once, even if the producer attempts to send it multiple times.
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Visibility timeout extension
Why it's wrong here
Extending the visibility timeout allows a consumer more time to process a message before it becomes visible to other consumers, preventing multiple consumers from processing the same message concurrently. While essential for preventing unintended duplicate processing due to long-running tasks, it does not prevent duplicate messages from being initially sent to the queue by a producer. Furthermore, it doesn't guarantee exactly-once processing if a consumer fails after processing but before deleting the message, as the message would eventually become visible again.

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DVA-C02 Development with AWS Services Practice Question

Why each option matters

Option-by-option breakdown

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