You are responsible for maintaining dozens of CloudFormation templates. Most of them use mappings to manage AMI IDs for different regions and instance types. However, the AMI IDs can change regularly, such as when there are software updates. In that case, you have to modify all related CloudFormation templates, which is very time-consuming. You are considering an automated method to query and get the correct AMI IDs for CloudFormation. Which two approaches together can help you achieve this? (Select TWO.)

Answer options:

A.Create a Lambda function to get the latest AMIs for a given region and instance type.
B.Prepare a shell script to fetch the latest AMIs for any region and instance type by using AWS CLI command such as ec2 describe-images.
C.In the CloudFormation template, create a custom resource type to invoke and send input values to a Lambda function to get the correct AMIs. After the custom resource gets a proper response, the stack proceeds with other resources.
D.Use a CloudWatch Event rule to execute a Lambda function every day to get the latest AMI IDs.
E.Add a new AMI ID parameter in the CloudFormation templates. When creating CloudFormation stacks, input the latest AMI ID parameter.

Correct Answer – A, C
The question asks for an automated method to fetch the AMI IDs for EC2 resources in the CloudFormation template. The manual methods should be avoided. Refer to https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/walkthrough-custom-resources-lambda-lookup-amiids.html for the suggested approach.
Option A is CORRECT: Because this Lambda function can use region and instance type as inputs and get the related AMIs. It then returns the IDs to the custom resource which is mentioned in Option
C.Option B is incorrect: Because there is no other option that can help execute the script in an automated way.
Option C is CORRECT: Because this custom resource can associate a Lambda function to get the AMI IDs. The stack can only proceed after the AMIs are received from the Lambda.
Option D is incorrect: Although the latest AMIs can be returned, there is no available option to provide the latest AMIs to CloudFormation templates.
Option E is incorrect: Because this needs manual intervention, which should be avoided considering the number of templates to maintain.