Question

A company stores the latest approved Amazon Linux 2 AMI ID in an SSM Parameter Store parameter named /golden/ami/linux2, which is updated weekly by an automated image-builder pipeline. A DevOps engineer maintains a CloudFormation template that launches EC2 instances and must always use the current value of this parameter at stack creation and update time — without editing the template or passing parameters manually. Which approach meets this requirement with the least ongoing effort?

Accepted Answer

Define a template parameter of type AWS::SSM::Parameter::Value<AWS::EC2::Image::Id> with a default of /golden/ami/linux2 so CloudFormation resolves the current value on each create/update operation.

Answer

Use a dynamic reference of the form {{resolve:ssm:/golden/ami/linux2}} directly in the ImageId property, which CloudFormation caches at first stack creation.

Answer

Add a Lambda-backed custom resource that reads the parameter with the SSM GetParameter API and returns the AMI ID to the EC2 resource on every stack event.

Answer

Create a CloudFormation macro that queries Parameter Store during template transformation and substitutes the AMI ID into the ImageId property.