Exam AWS Certified Developer Associate topic 1 question 19 discussion

The only plausible solution

A) Eliminated - Throttling would typically result in missing or delayed entries, not duplicates. B) Eliminated - SQS FIFO queues are designed to ensure exactly-once processing, C) Eliminated - API Gateway does not directly interact with SQS queues unless explicitly configured to do so. Even if API Gateway sends duplicate requests, the FIFO queue guarantees exactly-once delivery into the queue. Duplicates can only occur during processing, not from API Gateway itself. D) Correct - If the polling function's processing time (timeout) exceeds the visibility timeout, the message becomes visible again in the queue and can be reprocessed.

If the polling function’s execution time exceeds the visibility timeout, the message can be reprocessed, causing duplicate entries in the DynamoDB table.

If the time to process message is more than time visibility time out in the queue. The message will be touch twice

a message into FIFO can not be read by more than one process. The answer should be C

D - this is the only one that makes sense

OPTION D

for sure D

Does anyone raised a question like me, which is DynamoDB does not allow to have two identical items. So , this question itself is wrong?

I totally agree, the visibility timeout is an important parameter, if too short, a message can be processed twice or more....

This can happen because the message remains in the queue for a longer time, and it can be delivered to the same or another instance of the polling function again, which can result in duplicate items in the DynamoDB table. To resolve this issue, the developer can adjust the timeout settings and ensure that the queue visibility timeout is lower than the polling function's timeout. This will ensure that the message remains invisible to the queue for the desired time and is not delivered again during that period.

D is the answer

In a SQS FIFO queue, each message is processed exactly once and in the exact order it was added to the queue. However, in rare cases, a message might be delivered more than once, even when using a FIFO queue. This can happen if there is a delay in acknowledging the message or if the message times out before it can be deleted. In such cases, the message is returned to the queue and can be processed again by a consumer, resulting in duplicate processing of the same message. Option B I think

https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/FIFO-queues-exactly-once-processing.html

" If you don’t set the visibility timeout correctly, your message may be re-processed" https://tomgregory.com/3-surprising-facts-about-aws-sqs-fifo-queues/

If the function does not delete the message from SQS before the Visibility Timeout expires, another function will process the same message twice.

D It is very important to set the visibility timeout to a longer time because if the request does not get processed faster than the timeout, then it becomes visible again in the queue and its picked up by another service and reprocessed. This will result in duplicate processes.