Stack Designer

Quick Start

Design well-organized CloudFormation stacks with proper resource grouping, parameters, outputs, and cross-stack references.

Instructions

Step 1: Identify stack boundaries

Determine how to organize resources into stacks:

By lifecycle:

• Resources that change together should be in the same stack

• Separate frequently updated resources from stable infrastructure

• Group by deployment frequency

By ownership:

• Network stack (VPC, subnets, route tables)

• Security stack (security groups, IAM roles)

• Application stack (EC2, ECS, Lambda)

• Data stack (RDS, DynamoDB, S3)

By environment:

• Separate dev, staging, production stacks

• Use parameters for environment-specific values

• Share common resources via cross-stack references

Step 2: Design stack structure

Simple stack (single template):

AWSTemplateFormatVersion: '2010-09-09' Description: Simple web application stack

Parameters: EnvironmentName: Type: String Default: dev AllowedValues: [dev, staging, prod]

InstanceType: Type: String Default: t3.micro AllowedValues: [t3.micro, t3.small, t3.medium]

Resources: WebServer: Type: AWS::EC2::Instance Properties: InstanceType: !Ref InstanceType ImageId: !Sub '{{resolve:ssm:/aws/service/ami-amazon-linux-latest/amzn2-ami-hvm-x86_64-gp2}}' Tags: - Key: Environment Value: !Ref EnvironmentName

Outputs: InstanceId: Description: EC2 instance ID Value: !Ref WebServer Export: Name: !Sub '${AWS::StackName}-InstanceId'

Multi-stack architecture:

Root Stack ├── Network Stack (VPC, subnets) ├── Security Stack (security groups, IAM) ├── Database Stack (RDS) └── Application Stack (EC2, ALB)

Step 3: Define parameters

Parameter best practices:

Parameters:

Use descriptive names

DatabaseInstanceClass: Type: String Default: db.t3.micro AllowedValues: - db.t3.micro - db.t3.small - db.t3.medium Description: RDS instance class

Validate input

DatabaseName: Type: String MinLength: 1 MaxLength: 64 AllowedPattern: '[a-zA-Z][a-zA-Z0-9]*' ConstraintDescription: Must begin with letter, contain only alphanumeric

Use AWS-specific types

VpcId: Type: AWS::EC2::VPC::Id Description: VPC for resources

SubnetIds: Type: List<AWS::EC2::Subnet::Id> Description: Subnets for resources

Sensitive values from SSM

DatabasePassword: Type: AWS::SSM::Parameter::Value<String> Default: /myapp/database/password NoEcho: true

Step 4: Configure outputs

Output best practices:

Outputs:

Export for cross-stack references

VpcId: Description: VPC ID Value: !Ref VPC Export: Name: !Sub '${AWS::StackName}-VpcId'

Multiple values

PrivateSubnetIds: Description: Private subnet IDs Value: !Join [',', [!Ref PrivateSubnet1, !Ref PrivateSubnet2]] Export: Name: !Sub '${AWS::StackName}-PrivateSubnets'

Resource attributes

LoadBalancerDNS: Description: ALB DNS name Value: !GetAtt ApplicationLoadBalancer.DNSName

Conditional outputs

DatabaseEndpoint: Condition: CreateDatabase Description: RDS endpoint Value: !GetAtt Database.Endpoint.Address

Step 5: Implement cross-stack references

Exporting from one stack:

Outputs: SecurityGroupId: Value: !Ref WebSecurityGroup Export: Name: !Sub '${AWS::StackName}-SecurityGroupId'

Importing in another stack:

Resources: WebServer: Type: AWS::EC2::Instance Properties: SecurityGroupIds: - !ImportValue NetworkStack-SecurityGroupId

Nested Stacks

Parent stack:

Resources: NetworkStack: Type: AWS::CloudFormation::Stack Properties: TemplateURL: https://s3.amazonaws.com/mybucket/network.yaml Parameters: EnvironmentName: !Ref EnvironmentName Tags: - Key: Name Value: Network

ApplicationStack: Type: AWS::CloudFormation::Stack DependsOn: NetworkStack Properties: TemplateURL: https://s3.amazonaws.com/mybucket/application.yaml Parameters: VpcId: !GetAtt NetworkStack.Outputs.VpcId SubnetIds: !GetAtt NetworkStack.Outputs.SubnetIds

Benefits:

• Reusable templates

• Logical organization

• Independent updates

• Overcome template size limits

Common Patterns

Pattern 1: Environment-specific stacks

Use parameters for environment differences

Parameters: Environment: Type: String AllowedValues: [dev, staging, prod]

Mappings: EnvironmentConfig: dev: InstanceType: t3.micro MinSize: 1 MaxSize: 2 staging: InstanceType: t3.small MinSize: 2 MaxSize: 4 prod: InstanceType: t3.medium MinSize: 3 MaxSize: 10

Resources: AutoScalingGroup: Type: AWS::AutoScaling::AutoScalingGroup Properties: MinSize: !FindInMap [EnvironmentConfig, !Ref Environment, MinSize] MaxSize: !FindInMap [EnvironmentConfig, !Ref Environment, MaxSize] LaunchTemplate: LaunchTemplateId: !Ref LaunchTemplate Version: !GetAtt LaunchTemplate.LatestVersionNumber

Pattern 2: Conditional resources

Parameters: CreateDatabase: Type: String Default: 'true' AllowedValues: ['true', 'false']

Conditions: ShouldCreateDatabase: !Equals [!Ref CreateDatabase, 'true'] IsProduction: !Equals [!Ref Environment, 'prod']

Resources: Database: Type: AWS::RDS::DBInstance Condition: ShouldCreateDatabase Properties: DBInstanceClass: !If [IsProduction, db.t3.medium, db.t3.micro] MultiAZ: !If [IsProduction, true, false]

Pattern 3: Resource dependencies

Resources:

Explicit dependency

WebServer: Type: AWS::EC2::Instance DependsOn: DatabaseInstance Properties: # ...

Implicit dependency via Ref

SecurityGroupIngress: Type: AWS::EC2::SecurityGroupIngress Properties: GroupId: !Ref SecurityGroup SourceSecurityGroupId: !Ref LoadBalancerSecurityGroup

Stack Organization Strategies

Strategy 1: Layered architecture

Foundation Layer (rarely changes) ├── Network Stack (VPC, subnets, NAT) └── Security Stack (IAM roles, KMS keys)

Platform Layer (occasional changes) ├── Database Stack (RDS, ElastiCache) └── Storage Stack (S3, EFS)

Application Layer (frequent changes) ├── Compute Stack (EC2, ECS, Lambda) └── API Stack (API Gateway, ALB)

Strategy 2: Service-oriented

Per-service stacks: ├── User Service Stack ├── Order Service Stack ├── Payment Service Stack └── Shared Infrastructure Stack

Strategy 3: Environment isolation

Per-environment stacks: ├── Dev Environment │ ├── Network │ ├── Application │ └── Data ├── Staging Environment │ ├── Network │ ├── Application │ └── Data └── Production Environment ├── Network ├── Application └── Data

Advanced

For detailed information, see:

• Nested Stacks - Nested stack patterns and best practices

• Parameters - Parameter design and validation strategies

• Outputs - Output design and cross-stack references