Agent skill

cdk-patterns

AWS CDK patterns for TypeScript. Use when working with CDK infrastructure code. Do NOT use for Terraform, CloudFormation YAML, or other IaC tools. JavaScript is prohibited for CDK.

View SKILL.md on GitHub Repository
Stars 163
Forks 31

Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/cdk-patterns

SKILL.md

AWS CDK Patterns (TypeScript)

Patterns for AWS CDK infrastructure as code.

IMPORTANT: Always use TypeScript for CDK. JavaScript is prohibited.

Construct Separation: When to Do It

DO separate when:

  • Multiple instances needed in same Stack with different config
  • Organization-wide reuse as npm package
  • Unit testing a specific piece of infrastructure

DON'T separate when:

  • Single use within a Stack → function extraction is enough
  • No reuse planned → YAGNI
  • Simple composition → avoid over-engineering

Function extraction (often sufficient)

typescript
export class MyStack extends Stack {
  constructor(scope: Construct, id: string, props?: StackProps) {
    super(scope, id, props)

    const table = this.createDatabase()
    const api = this.createApi(table)
  }

  private createDatabase(): dynamodb.Table {
    return new dynamodb.Table(this, 'Table', { ... })
  }

  private createApi(table: dynamodb.Table): apigateway.RestApi {
    const handler = new lambda.Function(this, 'Handler', { ... })
    table.grantReadWriteData(handler)
    return new apigateway.RestApi(this, 'Api', { ... })
  }
}

Stack Design

Environment-based Stacks

typescript
// bin/app.ts
const app = new cdk.App()

const envConfig = {
  dev: { account: '111111111111', region: 'ap-northeast-1' },
  prod: { account: '222222222222', region: 'ap-northeast-1' },
}

new MyStack(app, 'MyStack-Dev', { env: envConfig.dev, stage: 'dev' })
new MyStack(app, 'MyStack-Prod', { env: envConfig.prod, stage: 'prod' })

Stack Props Pattern

typescript
interface MyStackProps extends StackProps {
  stage: 'dev' | 'staging' | 'prod'
}

export class MyStack extends Stack {
  constructor(scope: Construct, id: string, props: MyStackProps) {
    super(scope, id, props)

    const isProd = props.stage === 'prod'

    new dynamodb.Table(this, 'Table', {
      billingMode: isProd
        ? dynamodb.BillingMode.PROVISIONED
        : dynamodb.BillingMode.PAY_PER_REQUEST,
    })
  }
}

Props Design

Required vs Optional

typescript
interface MyConstructProps {
  // Required: no default makes sense
  tableName: string

  // Optional: sensible default exists
  readCapacity?: number
}

export class MyConstruct extends Construct {
  constructor(scope: Construct, id: string, props: MyConstructProps) {
    super(scope, id)

    const readCapacity = props.readCapacity ?? 5  // Default value
  }
}

Exposing Resources

typescript
export class MyConstruct extends Construct {
  // Expose for cross-construct references
  public readonly table: dynamodb.Table
  public readonly tableArn: string  // Convenience property

  constructor(scope: Construct, id: string) {
    super(scope, id)

    this.table = new dynamodb.Table(this, 'Table', { ... })
    this.tableArn = this.table.tableArn
  }
}

Testing with CDK Assertions

Snapshot Testing

typescript
import { Template } from 'aws-cdk-lib/assertions'

test('Stack matches snapshot', () => {
  const app = new cdk.App()
  const stack = new MyStack(app, 'TestStack')
  const template = Template.fromStack(stack)

  expect(template.toJSON()).toMatchSnapshot()
})

Resource Assertions

typescript
test('Creates DynamoDB table with correct config', () => {
  const app = new cdk.App()
  const stack = new MyStack(app, 'TestStack', { stage: 'prod' })
  const template = Template.fromStack(stack)

  template.hasResourceProperties('AWS::DynamoDB::Table', {
    BillingMode: 'PROVISIONED',
  })
})

test('Lambda has correct IAM permissions', () => {
  const template = Template.fromStack(stack)

  template.hasResourceProperties('AWS::IAM::Policy', {
    PolicyDocument: {
      Statement: Match.arrayWith([
        Match.objectLike({
          Action: Match.arrayWith(['dynamodb:GetItem', 'dynamodb:PutItem']),
        }),
      ]),
    },
  })
})

Resource Count

typescript
test('Creates expected number of Lambda functions', () => {
  const template = Template.fromStack(stack)
  template.resourceCountIs('AWS::Lambda::Function', 3)
})

Recommended Agent Skills

Expand your agent's capabilities with these related and highly-rated skills.

majiayu000/claude-skill-registry

agent-ops-spec

Manage specification documents in .agent/specs/. Use when user provides requirements, acceptance criteria, or feature descriptions that need to be tracked and validated against implementation.

163 31
Explore
majiayu000/claude-skill-registry

agent-ops-state

Maintain .agent state files. Use at session start, after meaningful steps, and before concluding: read/update constitution/memory/focus/issues/baseline consistently.

163 31
Explore
majiayu000/claude-skill-registry

agent-ops-spec

Manage specification documents in .agent/specs/. Use when user provides requirements, acceptance criteria, or feature descriptions that need to be tracked and validated against implementation.

163 31
Explore
majiayu000/claude-skill-registry

agent-ops-testing

Test strategy, execution, and coverage analysis. Use when designing tests, running test suites, or analyzing test results beyond baseline checks.

163 31
Explore
majiayu000/claude-skill-registry

agent-ops-testing

Test strategy, execution, and coverage analysis. Use when designing tests, running test suites, or analyzing test results beyond baseline checks.

163 31
Explore
majiayu000/claude-skill-registry

agent-ops-state

Maintain .agent state files. Use at session start, after meaningful steps, and before concluding: read/update constitution/memory/focus/issues/baseline consistently.

163 31
Explore

Didn't find tool you were looking for?

Be as detailed as possible for better results