- StackSet name:
demo-stack-set - Stack instances deployed to:
eu-west-1andus-east-1 - A single CloudFormation template that creates an S3 bucket; its name is derived from pseudoparameters so each instance gets a unique bucket name

- StackSet = master template + deployment settings
- Stack instance = per-region / per-account stack created from that template
- The template uses CloudFormation pseudoparameters
AWS::RegionandAWS::AccountIdvia!Sub. - Pseudoparameters are resolved at deployment time for each target account/region, producing unique bucket names per stack instance.
AWS::Region and AWS::AccountId. You can confirm those buckets in the S3 console.

How to verify deployments
- Open the CloudFormation console and inspect the StackSet’s “Stack instances” to see per-region/account status and Stack IDs.
- In each target region, open the S3 console to confirm the bucket names and creation dates.
- Review the StackSet template to see where pseudoparameters are used (for example, in
BucketName).
Pseudoparameters such as AWS::Region and AWS::AccountId are resolved at deployment time for each target account/region. That’s why names generated with !Sub are unique per stack instance.