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Top 20+ AWS CloudFormation Interview Questions & Answers

1. What is AWS CloudFormation?

CloudFormation is all about automating resource provisioning (Infrastructure as Code). So it simplifies the task of repeatedly and predictably creating groups of related resources that power your applications.

AWS CloudFormation offers a convenient way for developers and system administrators to create, manage, provision, and update a collection of related AWS resources in an orderly and predictable way.

  • Fully managed service
  • Create, update, and delete resources and sets known as stacks
  • Infrastructure as Code :

2. What are the benefits of AWS CloudFormation?

AWS CloudFormation is a service that helps you automate the process of creating and managing AWS infrastructure resources. It provides a number of benefits, including:

  • Automation: CloudFormation helps you automate the process of creating and managing resources, making it easier to create and maintain infrastructure.
  • Reusability: CloudFormation templates can be used to create stacks in multiple environments, such as development, staging, and production, allowing you to reuse your infrastructure definitions.
  • Version control: CloudFormation templates can be stored in version control systems, such as Git, allowing you to track changes to your infrastructure over time.
  • Collaboration: CloudFormation templates can be shared with other teams, allowing them to use your infrastructure definitions to create and manage their own resources.
  • Predictability: CloudFormation helps you create and manage resources in a predictable and orderly manner, reducing the risk of errors and ensuring that your resources are consistently and reliably deployed.
  • Resource management: CloudFormation allows you to manage all your resources as a single unit (a stack), making it easier to understand the relationships between your resources and to manage them as a whole.
  • Customization: CloudFormation allows you to customize the resources you create and the configuration of those resources, giving you more control over your infrastructure.

3. What is a circular dependency in AWS CloudFormation?

There is an interleaved dependency between two resources.

  • Resource X is dependent on Resource Y, and Resource Y is dependent on Resource X.
  • When this type of situation occurs, you will get a circular dependency error because AWS CloudFormation is unable to clearly determine which resource should be created first.
  • The AWS CloudFormation circular dependency can be caused by interactions between services that cause them to be mutually dependent.

4. How to solve circular dependency errors in AWS CloudFormation?

  • When two are dependent on one another we will get a circular dependency error because AWS CloudFormation is unable to clearly determine which resource should be created first
  • The first step is to examine the resources that are outlined and make sure that AWS CloudFormation can determine what resource order it should take.
  • To resolve a dependency error, add a DependsOn attribute to resources that depend on other resources in your template.
  • Using DependsOn, we can specify that a particular resource needs to be created before the other resource.

5. How can you create and delete stacks of AWS?

  • In AWS CloudFormation related resources are managed as a single unit called a stack.
  • It is possible to create, update, and delete a collection of resources by creating, updating, and deleting stacks.
  • All the resources in a stack are defined by the stack’s AWS CloudFormation template.

6. What does AWS Serverless Application Model add on top of CloudFormation?

AWS Serverless Application Model (SAM) is an open-source framework that provides additional functionality on top of AWS CloudFormation for building and deploying serverless applications. SAM extends CloudFormation to provide a simplified syntax for defining serverless resources, such as AWS Lambda functions and Amazon API Gateway APIs.

Using SAM, you can define your serverless resources in a template written in YAML, and then use the SAM CLI to package and deploy your application to AWS. SAM also provides tools for testing and debugging your serverless applications, as well as for managing the lifecycle of your application.

Some of the key benefits of using SAM on top of CloudFormation include:

  • Simplified syntax: SAM provides a concise and easy-to-use syntax for defining serverless resources in your template, reducing the complexity of writing CloudFormation templates.
  • Packaging and deployment: SAM provides tools for packaging and deploying your serverless application to AWS, simplifying the process of building and deploying your application.
  • Testing and debugging: SAM provides tools for testing and debugging your serverless application, including the ability to run your application locally and to generate sample event payloads for testing your functions.
  • Lifecycle management: SAM provides tools for managing the lifecycle of your serverless application, including the ability to update your application with zero downtime.

7. How does AWS Cloud Pipeline interact with CloudFormation?

You can use AWS CodePipeline to trigger a Cloud Formation template to run in the deployment phase.

The pipeline has the following stages:

  • Source phase: Fetch the latest commit.
  • Build phase: Build the code into a docker image and push it to ECR.
  • Deploy phase: Take the latest docker image from ECR, deploy it to ECS

8. How are shell scripts used with AWS CloudFormation templates?

EC2 instances can run shell scripts when they are launched using CloudFormation.

  • Provide commands in the user data section while launching an instance
  • If the instance is a part of the auto-scaling group, user data can also be provided using the launch configuration
  • We can use CodeDeploy for deploying apps on EC2 instances and it requires shell scripts to follow intended actions.

9. How does AWS CloudFormation work?

AWS CloudFormation is a service that helps you automate the process of creating and managing AWS infrastructure resources. It provides a common language for you to describe and provision infrastructure resources in your cloud environment.

Here’s how AWS CloudFormation works:

  1. You create a CloudFormation template that defines the resources you want to create in your AWS environment. The template is written in JSON or YAML and specifies the resources, their properties, and the dependencies between them.
  2. You use the AWS CloudFormation API or the AWS Management Console to create a new stack based on your template.
  3. AWS CloudFormation reads the template and creates the specified resources in your AWS account. If any resources depend on other resources, CloudFormation creates those resources first.
  4. AWS CloudFormation monitors the creation of the resources and rolls back the creation process if any errors occur.
  5. Once all the resources have been successfully created, AWS CloudFormation marks the stack as “CREATE_COMPLETE” and the resources are ready for use.
  6. You can make changes to your stack by updating the CloudFormation template and creating a new stack or updating the existing stack.
  7. When you no longer need the resources in your stack, you can delete the stack and AWS CloudFormation will delete all the resources associated with it.

Overall, AWS CloudFormation helps you automate the process of creating and managing resources in your AWS environment, making it easier to create and maintain infrastructure in a predictable and orderly manner.

10. What are the elements of an AWS CloudFormation template?

An AWS CloudFormation template is a JSON or YAML document that defines the infrastructure resources you want to create in your AWS environment. A template consists of six main elements:

  1. Resources: This element specifies the AWS resources that you want to create, such as Amazon EC2 instances, Amazon S3 buckets, and Amazon RDS databases. You can specify the properties of each resource, such as its type, name, and configuration.
  2. Parameters: This element allows you to specify input values that you can use to customize your template. You can use parameters to specify values such as the name of an Amazon S3 bucket or the size of an Amazon EC2 instance.
  3. Mappings: This element allows you to create a mapping of keys and values that you can use to specify resource properties or conditional logic in your template.
  4. Conditions: This element allows you to specify conditions that determine whether certain resources or resource properties should be created or included in your stack.
  5. Outputs: This element allows you to specify values that you want to return when you create or update a stack. You can use outputs to return values such as the public IP address of an Amazon EC2 instance or the URL of an Amazon S3 bucket.
  6. Metadata: This element allows you to specify additional information about your resources, such as the version of an AWS resource or the license of an application

CloudFormation Scenario-Based Interview Questions

11. What is the AWS CloudFormation Registry?

The CloudFormation registry lists the extensions, both private and public (AWS), that are available for use in your CloudFormation account. An extension is an artifact, registered in the CloudFormation Registry, which augments the functionality of CloudFormation in a native manner.

Third-party resource types must be registered before they can be used to provision resources with AWS CloudFormation templates. Please see Using the AWS CloudFormation registry in our documentation for details.

12. How is AWS CloudFormation different from AWS Elastic Beanstalk?

AWS CloudFormation and AWS Elastic Beanstalk are both tools provided by Amazon Web Services (AWS) that can be used to deploy and manage applications in the cloud. However, they have some key differences:

  • Purpose: CloudFormation is a infrastructure-as-code service that allows you to define and provision infrastructure resources in your AWS environment using templates written in JSON or YAML. Elastic Beanstalk is a platform-as-a-service (PaaS) that allows you to deploy and manage applications without the need to worry about the underlying infrastructure.
  • Resource creation: CloudFormation creates and manages individual resources in your AWS environment, such as Amazon EC2 instances, Amazon S3 buckets, and Amazon RDS databases. Elastic Beanstalk creates and manages an entire environment for your application, including resources such as EC2 instances, Auto Scaling groups, and Amazon RDS DB instances.
  • Deployment process: CloudFormation requires you to create a stack and then specify the resources you want to create in that stack. Elastic Beanstalk automatically creates and manages the necessary resources for your application, and you simply need to upload your application code.
  • Customization: CloudFormation allows you to customize the resources you create and the configuration of those resources. Elastic Beanstalk provides some customization options, but is generally more opinionated and does not allow as much control over the underlying infrastructure.

Overall, CloudFormation is a more flexible and powerful tool for managing infrastructure in your AWS environment, while Elastic Beanstalk is a simpler and more opinionated tool for deploying and managing applications. Depending on your needs, you may choose to use one or both of these tools in your AWS environment.

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AWS CloudFormation Interview Questions

13. Explain AWS CloudFormation Features.

AWS CloudFormation gives you an easy way to model a collection of related AWS and third-party resources, provision them quickly and consistently, and manage them throughout their lifecycles, by treating infrastructure as code.

  • Extensibility – You can build your own resource providers using the AWS CloudFormation CLI, an open-source tool that streamlines the development process, including local testing and code generation capabilities.
  • Cross account & cross-region management – CloudFormation StackSets let you provision a common set of AWS resources across multiple accounts and regions, with a single CloudFormation template. StackSets takes care of automatically and safely provisioning, updating, or deleting stacks, no matter where they are.
  • Authoring with JSON/YAML – CloudFormation allows you to model your entire cloud environment in text files. You can use open-source declarative languages, such as JSON or YAML, to describe what AWS resources you want to create and configure.
  • Safety controls – CloudFormation automates provisioning and updating your infrastructure in a safe and controlled manner. There are no manual steps or controls that can lead to errors.
  • Dependency management – AWS CloudFormation automatically manages dependencies between your resources during stack management actions.

14. Explain the three basic types of cloud services.

The three basic types of cloud services are:

  • Computing – These include EC2, Elastic Beanstalk, Lambda, Auto-Scaling, and Lightsail.
  • Storage – These include S3, Glacier, Elastic Block Storage, and Elastic File System.
  • Networking – These include VPC, Amazon CloudFront, Route53

15. Difference between the SAM template and the Cloudformation template?

SAM templates are an extension of AWS CloudFormation templates, with some additional components that make them easier to work with. For the full reference for AWS CloudFormation templates, see AWS CloudFormation Template Reference in the AWS CloudFormation User Guide.

Cloudformation template is a declaration of the AWS resources that make up a stack. The template is stored as a text file whose format complies with the JavaScript Object Notation (JSON) or YAML standard. In the template, you declare the AWS resources you want to create and configure.

16. What happens when one of the resources in a stack cannot be created successfully?

By default, the automatic rollback on the error feature is enabled. This will direct CloudFormation to only create or update all resources in your stack if all individual operations succeed. If they do not, CloudFormation reverts the stack to the last known stable configuration.

For example, if you accidentally exceed your default limit of Elastic IP addresses, or you do not have access to an EC2 AMI that you are trying to run. This feature enables you to rely on the fact that stacks are created either fully or not at all, which simplifies system administration and layered solutions built on top of CloudFormation.

17. What can developers do with AWS CloudFormation?

AWS CloudFormation is a service that gives developers and businesses a possible way to create a collection of related AWS and third-party resources, and provision and manages them in an orderly and predictable fashion.

Developers can deploy and update compute, database, and many other resources in a simple, declarative style that abstracts away the complexity of specific resource APIs. AWS CloudFormation is designed to allow resource lifecycles to be managed repeatably, predictably, and safely, while allowing for automatic rollbacks, automated state management, and management of resources across accounts and regions.

18. What are the steps involved in a CloudFormation Solution?

Here are the steps involved in a CloudFormation solution:

  • Create or use an existing CloudFormation template using JSON or YAML format.
  • Save the code in an S3 bucket, which serves as a repository for the code.
  • Use AWS CloudFormation to call the bucket and create a stack on your template.
  • CloudFormation reads the file and understands the services that are called the relationship between the services, and provisions the services one after the other.

19. On top of CloudFormation, what does AWS Serverless Application Model offer?

An Open Source framework that can help create serverless apps on AWS is an AWS Serverless Application Model.

AWS SAM has an application description template for the serverless application, AWS SAM is an extension to AWS CloudFormation’s Template language that enables you to set AWS Lambda applications without servers, on a higher level. CloudFormation is supported in the service configuration. It automates common tasks such as building functional roles, making it easier for your serverless applications to type out CloudFormation templates.

20. What exactly is the Amazon Web Services CloudFormation Registry?

The CloudFormation registry lists the extensions available for use in your CloudFormation account, both private and public (AWS). An extension is an artifact, registered in the CloudFormation Registry that augments CloudFormation’s native functionality.

Before third-party resource types can be used to provide services with AWS CloudFormation models, they must first be recorded. Amazon, APN partners, Marketplace sellers, and the developer community may all build extensions. CloudFormation items like resource types and modules are examples of extensions.

21. Cloudformation template Vs SAM template?

Cloudformation template SAM template

The AWS resources that make up a stack are declared in a Cloudformation template.SAM templates are an extension of AWS CloudFormation templates that include some additional components that make them easier to use.
The template is saved as a text file that follows the JavaScript Object Notation (JSON) or YAML format standards. You declare the AWS resources you want to build and configure in the template.Allows you to define serverless AWS Lambda applications at a higher level. It automates common tasks such as function role creation and makes it easier to write CloudFormation templates for your serverless applications.

22. Describe the three main types of cloud services.

The three primary forms of cloud services are as follows:

  • Computing:¬†services such as EC2, Elastic Beanstalk, Lambda, Auto-Scaling, and Lightsail are examples.
  • Storage: S3, Glacier, Elastic Block Storage, and Elastic File System are examples of storage services.
  • Networking:¬†VPC, Amazon CloudFront, and Route53 are examples of networking services.

23. What is AWS CloudFormation Template?

Templates are JSON or YAML formatted text files. AWS CloudFormation uses JSON or YAML format file to describe the collection of AWS resources (known as a stack), their associated dependencies, and any required runtime parameters are called CloudFormation Template

  • Text File
  • JSON or YAML format
  • Self-documenting environment
  • Resources to provision

Below is a basic AWS CloudFormation YAML-formatted template fragment. Templates contain parameters, resource declarations, and outputs. Templates can reference the outputs of other templates, which enables modularization.

---
AWSTemplateFormatVersion: "version date"Description:
 String
Parameters:
 set of parameters
Mappings:
 set of mappings
Conditions:
 set of conditions
Transform:
 set of transforms
Resources:
 set of resources
Outputs:
 set of outputs

Here is an example of an AWS CloudFormation template. The template requests the name of an Amazon Elastic Compute Cloud (EC2) key pair from the user in the parameters section.2 The resources section of the template then creates an EC2 instance using that key pair, with an EC2 security group that enables HTTP (TCP port 80) access.

Parameters:KeyName:Description: The EC2 key pair to allow SSH access to the
instance
 Type: AWS::EC2::KeyPair::KeyName
Resources:Ec2Instance:Type: AWS::EC2::Instance
 Properties:SecurityGroups:!Ref InstanceSecurityGroup
 KeyName:!Ref KeyName
 ImageId: ami-70065467
 InstanceSecurityGroup:Type: AWS::EC2::SecurityGroup
 Properties:GroupDescription: Enable HTTP access via port 80
 SecurityGroupIngress:
 - IpProtocol: tcp
 FromPort: '80'ToPort: '80'CidrIp: 0.0.0.0/0

24. How does AWS Cloud Pipeline interact with CloudFormation?

You can use AWS Code Pipeline to run a Cloud Formation template in the deployment phase. The pipeline has the following stages:

  • Source phase: Get the latest commit.
  • Build phase: Build the code into a docker image and push it to ECR.
  • Deploy phase: take the latest docker image from ECR, and deploy it to ECS.

25. What is Infrastructure as Code and its Benefits?

Infrastructure as code is a technique whereby we create machine-readable files that describe our infrastructure.

Now there are many different technologies to do Infrastructure as code, and AWS CloudFormation is one example. AWS CloudFormation, you can maintain your infrastructure just like application source code.

Infrastructure as Code Benefits :
  • By codifying Infrastructure, which is describing it within a file, we have a way of including it within our source control solution. We can check in the files into GitHub or whatever source control solution we’re using. This makes it much easier to maintain the infrastructure, as we have the full power of the source control system to handle modifications to certain files. It makes deployments a lot smoother, too. Since the infrastructure is specified inside a file, it can be securely and continuously deployed over and over again.
  • In our build and release pipeline, we can also include it. So, as our application is deployed to the cloud, it is also possible to deploy any changes required to the infrastructure at the same time. It helps avoid what is known as environmental drift from occurring.
  • For testers, infrastructure as a code often provides advantages. Test teams have early access to production-like test environments, and an entirely new test environment that is very easily similar to the production environment can be spin up. This may be for load testing or penetration testing. When done, it is possible to break down and discard the environment.
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26. What steps are involved in implementing a CloudFormation Solution?

These are the steps to a solution for CloudFormation:

  1. To begin, we must code our infrastructure in a YAML or JSON text-based file known as a template to create a CloudFormation template.
  2. Then we write our code locally in the AWS CloudFormation tool. Otherwise, we can use the S3 bucket to store a YAML or JSON file that will act as a repository for the code.
  3. Then, using the AWS CF GUI or the Command Line Interface, create a stack based on our template code by calling the bucket.
  4. CloudFormation reads the file and recognizes the services, also known as the relationship between the services, before provisioning the services one after the other.
  5. Finally, CloudFormation deploys resources, provisions them, and configures them according to the template we specified.

27. what is the difference between AWS CloudFormation vs Elastic Beanstalk?

Here is a comparison of AWS CloudFormation and AWS Elastic Beanstalk:

FeatureCloudFormationElastic Beanstalk
PurposeInfrastructure as codePlatform as a service
Resource creationIndividual resourcesComplete environment
Deployment processCreate stackUpload application
CustomizationHighLow
Resource managementStackEnvironment
AutomationHighLow
OpinionatedLowHigh

AWS CloudFormation is a infrastructure-as-code service that allows you to define and provision infrastructure resources in your AWS environment using templates written in JSON or YAML. Elastic Beanstalk is a platform-as-a-service (PaaS) that allows you to deploy and manage applications without the need to worry about the underlying infrastructure.

28. How do you create and delete AWS stacks?

You can create and delete AWS stacks using AWS CloudFormation. Here’s how the process works:

  1. To create a stack, you need to first create a CloudFormation template that defines the resources you want to create in your AWS environment. The template is written in JSON or YAML and specifies the resources, their properties, and the dependencies between them.
  2. Once you have your template ready, you can use the AWS Management Console, the AWS CloudFormation API, or the AWS CloudFormation CLI to create a new stack. You will need to specify the name of your stack and the location of your template, as well as any parameters or capabilities that are required.
  3. AWS CloudFormation will then create the resources specified in your template and monitor the creation process. If any errors occur, the stack creation will be rolled back.
  4. Once all the resources have been successfully created, AWS CloudFormation will mark the stack as “CREATE_COMPLETE” and the resources will be ready for use.
  5. To delete a stack, you can use the AWS Management Console, the AWS CloudFormation API, or the AWS CloudFormation CLI to delete the stack. AWS CloudFormation will then delete all the resources associated with the stack.

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