Inside a resource property, a template should read a database endpoint that is stored in SSM Parameter Store, and it should do so at deploy time without declaring a template parameter. Which syntax accomplishes this?
Show answer and explanation
Answer: B
A dynamic reference using the resolve:ssm pattern tells CloudFormation to fetch the parameter value when it applies the resource property, so no template parameter is needed. Dynamic references are used directly in resource properties and resolve during stack operations. The secure variant, resolve:ssm-secure, is limited to certain properties, so it is not the default choice for every value.
Why the other options are wrong
- A. Fn::ImportValue reads an export that another stack has published. It works between stacks and does not look up a value in Parameter Store.
- C. FindInMap returns values from a static Mappings section in the template. Those values are written into the template, not fetched from SSM at deploy time.
- D. Join only concatenates strings. It cannot retrieve a parameter's stored value, so the endpoint would never be resolved.