Exam AWS DevOps Engineer Professional topic 1 question 3 discussion

I'll go with B because it is right Reference: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/crpg-ref-responses.html

When AWS CloudFormation invokes a Lambda function using a custom resource, it provides a pre-signed URL as part of the request. The Lambda function must return a response to the pre-signed URL to signal the success or failure of the resource creation. If the Lambda function does not return a response to the pre-signed URL, the CloudFormation stack will remain in the CREATE_IN_PROGRESS state, waiting for a response.

There is no mention of S3 so why are using pre signed url? Seems that D is a better option

Yes B is Correct

Yes B is Correct Custom Resources needs a response to provided through Lambda

Answer is B- Cloudformation expect the Lambda function invoked using a custom resource to call back at the signed URL

these passed to the lambda as event and invoked : { "RequestType" : "Create", "ResponseURL" : "http://pre-signed-S3-url-for-response", "StackId" : "arn:aws:cloudformation:us-west-2:123456789012:stack/stack-name/guid", "RequestId" : "unique id for this create request", "ResourceType" : "Custom::TestResource", "LogicalResourceId" : "MyTestResource", "ResourceProperties" : { "Name" : "Value", "List" : [ "1", "2", "3" ] } } and the response has to have: event['ResponseURL']

B I thinks its B as Cloudformation stack needs to be updated of the status using helper scripts

I think its A it's not enough with code returns a response to the pre-signed URL it would need to be successfully

Option A is broad but could be the right answer. For option B, I'm skeptical as it says "pre-signed URL" (which is for S3) instead of callback URL or ResponseURL.

The answer is B As noted in the CloudFormation documentation, CloudFormation expects your Lambda function to callback to it once it has completed its operation; CloudFormation will pause execution until this callback is received. The event sent to your Lambda function by CloudFormation contains the callback URL (ResponseURL)

I'd say B, but the question is a bit light on details. https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-lambda-function-code-cfnresponsemodule.html

I will go with D