As a developer, you have created a Lambda function used to work with a bucket in Amazon S3. The Lambda function is not working as expected. You need to debug the issue and understand what’s the underlying issue. How can you accomplish this in an easily understandable way?

Answer options:

A.Use AWS CloudWatch metrics.
B.Use AWS CloudWatch logs.
C.Raise a ticket with the AWS Support team.
D.Use AWS CloudTrail logs.

Answer – B
This is also mentioned in the AWS Documentation.
You can insert logging statements into your code to help you validate that your code is working as expected. Lambda automatically integrates with Amazon CloudWatch Logs and pushes all logs from your code to a CloudWatch Logs group associated with a Lambda function (/aws/lambda/). 
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 since there is no need to raise a support ticket with the AWS support team.
Option D is incorrect since this is only used for API monitoring.
For more information on monitoring functions, please refer to the below URL-
https://docs.aws.amazon.com/lambda/latest/dg/monitoring-functions.html