Exam AWS Certified Developer - Associate DVA-C02 topic 1 question 268 discussion

The problem is the Lambda processes the message multiple times. This is due to Lambda concurrency mixed with VisibilityTimeout of the SQS queue. VisibilityTimeout defaults to 30 seconds. Using this default, if the Lambda takes longer than 30 seconds to process the message, then the message will become available again in the Queue for consumers. This means a second Lambda can come along and dequeue the same message - leading to duplicate processing. This problem can be solved with A or C However - the question is asking for MOST cost effective The answer MUST be C then: using Lambda Reserved Concurrency (totally free).

A is the correct answer.

The actual answers are not mentioned into the options as most cost effective remedy https://docs.aws.amazon.com/lambda/latest/dg/with-sqs.html#services-sqs-batchfailurereporting:~:text=To%20prevent%20Lambda,successfully%20processes%20them.

B is correct Because of Cost

Given this, based on AWS best practices, changing the Amazon SQS standard queue to an Amazon SQS FIFO (First-In, First-Out) queue using the Amazon SQS message deduplication ID (Option A) is the most effective way to ensure messages are processed once and in the order they are sent. FIFO queues are designed to prevent duplicate processing and maintain the order of messages, which aligns with the requirement to resolve the issue of Lambda functions processing some messages multiple times.

In this case most cost effective option

A is correct.