Exam AWS Certified Developer Associate topic 1 question 169 discussion

Option B is not the best solution for this use case because it involves creating an ongoing Amazon EventBridge (Amazon CloudWatch Events) rule with a rate expression of 600 seconds. This means that the rule would trigger the Lambda function every 600 seconds (10 minutes) regardless of whether a new account registration has occurred or not. In contrast, Option C allows you to trigger the Lambda function specifically 10 minutes after a new account registration by sending a message to an Amazon Simple Queue Service (Amazon SQS) delay queue and setting the queue to 600 seconds. This way, the Lambda function is only invoked when a new account registration occurs, and not on an ongoing basis. This is why Option C is a better solution for this use case.

In my opinion is B because we need event-driven policy that can be configured with CloudWatch Events

I think they are asking about the orchestration with the messages (they use the word "event" to mislead, because that`s the business of the company). Message timers let you specify an initial invisibility period for a message added to a queue (between 0 seconds and 15 minutes). https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-message-timers.html

I think they are asking about the orchestration with the messages (they use the word "event" to mislead, because that`s the business of the company). Message timers let you specify an initial invisibility period for a message added to a queue (between 0 seconds and 15 minutes). https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-message-timers.html

with B the lambda function will be called at certain time intervals, in this case. it will be every 10 mins. And the user registration event is not in play in this mechanism. the requirement requires an event-driven mechanism with a certain delay. so it's C.

IMO, SQS would complicate things a lot: Lambda has to read from the SQS. I am going with B

*signle invocation* - C scheduled - B

it's B, not C because using SQS delay queue would also introduce a 10-minute delay, but it involves an extra step of sending a message to SQS and using it as an event source for the Lambda function.

C, bz rate expression is for scheduled events.

B for sure - EventBridge. It is not C because the purpose of delay queues in SQS is totally different. Their use case is when your consumer application needs additional time to process messages. Although they might still work in this case, it would be a temporary and hacky kind of solution. And imagine the delay requirement changing in the future and now you need to invoke the lambda function 20 minutes later, then the delay queue won't work as its maximum delay is limited to 15 mins.

B is better for this use case

Any idea why not A?

delay queue to hide the message for first 10 mins

I'd say C

https://docs.aws.amazon.com/AWSSimpleQueueService/latest/SQSDeveloperGuide/sqs-delay-queues.html

https://docs.aws.amazon.com/eventbridge/latest/userguide/eb-run-lambda-schedule.html

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