Environment Parity

Environment Parity

Overview

Environment parity means using the same infrastructure code across all environments, with only configuration values changing. This reduces "works on my machine" problems and ensures production behavior is tested before deployment.

graph LR
    subgraph "Single Codebase"
        Code[Infrastructure Code]
    end
    
    subgraph "Configurations"
        Dev[dev.tfvars]
        Staging[staging.tfvars]
        Prod[prod.tfvars]
    end
    
    subgraph "Environments"
        DevEnv[Development]
        StagingEnv[Staging]
        ProdEnv[Production]
    end
    
    Code --> Dev --> DevEnv
    Code --> Staging --> StagingEnv
    Code --> Prod --> ProdEnv

What Should Differ

What Should NOT Differ

• ✅ Resource types and structure
• ✅ Security group rules (ports, protocols)
• ✅ IAM policy structure
• ✅ Encryption settings
• ✅ Network topology

Best Practices

1. Single source of truth - One codebase, multiple configs
2. Use tfvars/context - Environment-specific settings
3. Conditional logic sparingly - Prefer configuration over conditionals
4. Match production - Staging should mirror prod closely
5. Test in lower environments first - Dev → Staging → Prod

Example 1: Terraform - Workspaces + Variable Files

Environment parity with workspace isolation and tfvars files.

📁 Location: terraform/examples/environment-parity/

Configuration Files

# environments/dev.tfvars
environment = "dev"
instance_type = "t3.small"
rds_instance_class = "db.t3.micro"
rds_multi_az = false
rds_deletion_protection = false
min_capacity = 1
max_capacity = 2
enable_enhanced_monitoring = false

# environments/prod.tfvars
environment = "prod"
instance_type = "t3.large"
rds_instance_class = "db.r5.large"
rds_multi_az = true
rds_deletion_protection = true
min_capacity = 3
max_capacity = 10
enable_enhanced_monitoring = true

Usage

# Deploy to dev
terraform workspace select dev
terraform apply -var-file="environments/dev.tfvars"

# Deploy to prod
terraform workspace select prod
terraform apply -var-file="environments/prod.tfvars"

Example 2: CDK - Context-Based Configuration

Environment parity using CDK context for configuration.

📁 Location: cdk/examples/environment-parity/

Context Configuration

// cdk.json
{
  "context": {
    "dev": {
      "instanceType": "t3.small",
      "rdsInstanceClass": "db.t3.micro",
      "multiAz": false,
      "minCapacity": 1,
      "maxCapacity": 2
    },
    "prod": {
      "instanceType": "t3.large",
      "rdsInstanceClass": "db.r5.large",
      "multiAz": true,
      "minCapacity": 3,
      "maxCapacity": 10
    }
  }
}

// app.ts
const environment = app.node.tryGetContext('environment') || 'dev';
const config = app.node.tryGetContext(environment);

new MyStack(app, `MyApp-${environment}`, {
  ...config,
  environment,
});

Usage

# Deploy to dev
cdk deploy --context environment=dev

# Deploy to prod
cdk deploy --context environment=prod

Validation Checklist

• Same Terraform/CDK code deploys to all environments
• Only configuration values differ (sizes, counts, retention)
• Security configurations are consistent
• Staging closely matches production
• Changes tested in dev/staging before prod

Related Skills

• Layered Stacks - Layers per environment
• GitOps Workflow - Environment promotion
• Remote State Boundaries - State per env