Applying CloudFormation StackSets across multiple accounts and AWS Regions

What are AWS CloudFormation StackSets and how do they benefit multi-account and multi-region management?

AWS CloudFormation StackSets allow you to create, update, or delete stacks across multiple accounts and regions with a single operation. They simplify the management of AWS resources across different accounts and regions by enforcing consistency, reducing the potential for errors, and saving time for DevOps teams.

How do CloudFormation StackSets differ from standard CloudFormation stacks?

CloudFormation StackSets extend the functionality of individual stacks by enabling you to deploy the same stack across multiple AWS accounts and regions. They handle the operations in a coordinated way, ensuring that stacks are deployed consistently, whereas standard CloudFormation stacks manage resources within a single account and region.

Can you describe the permission model used by CloudFormation StackSets for deploying stacks across multiple accounts?

CloudFormation StackSets use a service-managed or self-managed permissions model. With service-managed permissions, AWS Organizations is leveraged to automatically deploy to accounts within an organization or organizational units (OUs). With self-managed permissions, you manually set up IAM roles in the target accounts to grant StackSets the necessary permissions.

What are the key considerations when choosing between service-managed and self-managed permission models in StackSets?

The key considerations include the level of control required, the structure of your AWS accounts, and whether you’re using AWS Organizations. Service-managed permissions provide a simpler setup for those using AWS Organizations, while self-managed permissions offer more granular control over IAM roles and are necessary for accounts outside of AWS Organizations.

How would you monitor the status of your stack instances across multiple accounts and regions?

You can monitor the status of stack instances within CloudFormation in the AWS Management Console or use the CloudFormation APIs. Additionally, you may integrate CloudFormation with Amazon CloudWatch to trigger alarms or notifications based on stack events.

When deploying a StackSet, what strategies can you use to prevent service interruptions or deployment failures in multiple regions?

You can use various strategies such as deploying in batches, staggering deployments across regions, employing AWS Region Concurrency controls, and using failure tolerance settings to prevent widespread impact. Additionally, testing changes in a staging environment before production deployment can reduce the likelihood of interruptions.

Explain how you would roll back a change that caused issues after applying a StackSet operation to multiple regions/accounts.

To roll back a change, you can use the StackSets operation to issue an update with the previous, known-good template and parameters. If you have configured automatic rollback on stack operation failure, CloudFormation will attempt to roll back to the previous state in the event of a failure.

Describe how you would update a particular stack instance within a StackSet while leaving others unchanged.

To update a specific stack instance, you can initiate an update StackSet operation and select the Regions and account(s) for the stack instances that you want to update, or use override operations if only certain parameters need to change for specific instances.

How does CloudFormation StackSets handle drift detection, and what are the implications for stacks across multiple accounts and regions?

CloudFormation StackSets support drift detection to identify discrepancies between the stack’s actual configuration and its expected configuration. Drift detection helps in maintaining consistency across multiple accounts and regions by alerting you to unauthorized or accidental changes so that you can take appropriate action.

What are the limitations of using AWS CloudFormation StackSets?

Some limitations include a maximum number of stack instances that can be managed, restrictions on updating stack sets with service-managed permissions, lack of support for all AWS resources, and the complexity of managing stack set operations as the number of accounts and regions grow.

Remember that these answers are guidelines and additional elaboration with personal experience, if possible, would be beneficial during an interview. Since the AWS platform is frequently updated, be sure to check the latest AWS documentation before your interview to ensure that the information given is still accurate.