You have a lambda function that is processed asynchronously. You need a way to check and analyse issues if the function fails, for further processing at a later time. How could you accomplish this?

Answer options:

A.Use AWS CloudWatch metrics.
B.Assign a dead letter queue.
C.Configure CloudWatch Events.
D.Use AWS CloudTrail logs.

Answer – B
This is also mentioned in the AWS Documentation.
Any Lambda function invoked asynchronously is retried twice before the event is discarded. If the retries fail and you`re unsure why use Dead Letter Queues (DLQ) to direct unprocessed events to an Amazon SQS queue to analyze the failure.
Option A is incorrect since the metrics will only give the rate at which the function is executing. But it cannot help debug the actual error.
Option C is incorrect because CloudWatch Events cannot help to handle failed or discarded events.
Option D is incorrect since this is only used for API monitoring.
For more information on dead letter queues with AWS Lambda, please refer to the below URL-
https://docs.aws.amazon.com/lambda/latest/dg/dlq.html