You are in charge of maintaining several AWS CloudFormation StackSets in a large organization. One StackSets was created to configure infrastructure resources such as IAM roles and security groups in several regions for a web application. Recently, due to certain new features of the application, one parameter value of the CloudFormation StackSets needs to be updated. However, this update is only required for two regions and the other regions should not be changed for the parameter. How should you implement this?

Answer options:

A.Parameters of StackSets can only be modified for all regions. This operation cannot be done unless the CloudFormation stacks in these two regions are removed from the StackSets.
B.Parameters of StackSets can not be modified for selected regions. Deregister these two regions from the StackSets and then create a new StackSet with new parameters in these two regions.
C.Choose Override StackSet parameters from the Actions menu. Specify the two regions that you want to modify and then override the StackSet parameters for these regions.
D.Choose Edit StackSet Details from the Actions menu. Specify the two regions that you want to change and then modify the StackSet parameters for only these two regions.

Correct Answer – C
In this case, stack instances in two regions need to have different property values than the specified ones when the StackSets was created. This can be done by overriding parameter values for existing stack instances. The detailed explanation can be found in https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/stackinstances-override.html.
Option A is incorrect: Because parameters of StackSets can be overridden in selected regions. Users do not need to remove stacks from StackSets.
Option B is incorrect: Because it is unnecessary to create new StackSets for updating parameters.
Option C is CORRECT: Because you can specify particular regions where parameters need to be modified. Take below screenshots for an example:
1, Select the StackSet and choose Override StackSet parameters.
2, Specify the accounts and regions.
3, Edit the value to true for EnableLogFileValidation.
Option D is incorrect: Because Edit StackSet Details action modifies the parameter values in all regions for the whole StackSet. Refer to
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/stacksets-update.html
for details. In this question, Override StackSet parameters should be used.