DOP-C02 Practice Question 5: Change Set Preview Before Update
AWS Certified DevOps Engineer – Professional (DOP-C02) · Test 1 · question 5 of 10
Before applying a template change to a production CloudFormation stack, a release engineer needs to know whether the update will replace the stack's Amazon RDS DB instance, a replacement would destroy the database, or merely modify it in place. The engineer must be able to see this before any resource is touched.
Which CloudFormation feature provides this information?
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Answer:
A change set is a preview: CloudFormation compares the proposed template and parameters against the current stack and returns the list of resource changes it *would* make, without making any of them. Each entry carries an Action (Add, Modify, Remove, Import) and, for Modify, a Replacement value of True, False, or Conditional. Seeing Replacement: True on the AWS::RDS::DBInstance is precisely the signal the engineer needs, and the change set can simply be deleted instead of executed.
Option A answers a different question. Drift detection reports where the *live* resources have diverged from the template that was last deployed, changes made out of band, in the console or CLI. It says nothing about what a future template change would do.
Option C protects the resource but does not inform. A stack policy denying Update:Replace will cause the update to fail when it reaches that resource, after CloudFormation has already begun the update and possibly modified other resources, and then roll back. That is a guardrail, not a preview, and the stem requires knowing before anything is touched.
Option D is worse still: --disable-rollback removes the safety net, the update is genuinely under way, and by the time a DB instance shows UPDATE_IN_PROGRESS a replacement may already be provisioning. Cancelling mid-update leaves the stack in UPDATE_ROLLBACK_* states rather than preventing the change.
Reference: Update stacks using change sets