How should the developer reference the parameter that contains the database hostname?
Use the ssm dynamic reference.
Use the Ref intrinsic function.
Use the Fn::ImportValue intrinsic function.
Use the ssm-secure dynamic reference.
Explanations:
The ssm dynamic reference is used to reference a parameter from AWS Systems Manager Parameter Store in CloudFormation templates. It allows CloudFormation to retrieve the value of the parameter at stack creation time, which in this case, is the plaintext hostname of the RDS database.
The Ref intrinsic function is used to reference resources or parameters that are directly defined in the CloudFormation template (like a resource name or output value). It cannot be used to reference a Systems Manager Parameter Store value.
The Fn::ImportValue function is used to import values from another CloudFormation stack’s output. This is not applicable in this case because the RDS hostname is stored in Parameter Store, not as an output of another stack.
The ssm-secure dynamic reference is used to reference parameters in Systems Manager Parameter Store that are stored as SecureString (encrypted) values. Since the database hostname is stored as plaintext, the ssm dynamic reference (Option A) is the correct choice.
I judge that the answer is:
Use the ssm dynamic reference.