Introduction to AWS CDK

The AWS Cloud Development Kit (CDK) is an open-source framework that lets you define cloud infrastructure using familiar programming languages. Instead of writing YAML or JSON templates, you use TypeScript, Python, Java, C#, or Go to define your resources. Under the hood, the CDK generates CloudFormation templates, so you get all the benefits of CloudFormation — dependency resolution, rollback, drift detection — combined with the full power of a programming language.

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Why CDK?

CloudFormation templates are powerful but have limitations:

• Verbosity — even simple architectures require hundreds of lines of YAML
• No abstraction — you cannot create reusable functions or classes in YAML
• No loops — you cannot iterate over a list to create multiple similar resources
• Limited testing — YAML templates are difficult to unit test
• No IDE support — no autocomplete, no type checking, no refactoring tools

The CDK addresses all of these by letting you use a real programming language.

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How the CDK Works

The CDK workflow has three layers:

1. CDK App

Your CDK code is a regular application written in TypeScript, Python, or another supported language. It defines one or more stacks.

2. Synthesis (cdk synth)

When you run cdk synth, the CDK compiles your code into a CloudFormation template (called a cloud assembly). This is the "translation" step.

3. Deployment (cdk deploy)

When you run cdk deploy, the CDK submits the synthesised CloudFormation template to AWS, which creates or updates the stack.

CDK Code (TypeScript) → cdk synth → CloudFormation Template (YAML) → cdk deploy → AWS Resources

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CDK Concepts

Constructs

Constructs are the basic building blocks of a CDK app. Every resource, group of resources, or abstraction is a construct.

There are three levels of constructs:

Level	Name	Description
L1	CFN Resources	Direct 1:1 mapping to CloudFormation resources (e.g., CfnBucket)
L2	Curated Constructs	Higher-level abstractions with sensible defaults (e.g., Bucket)
L3	Patterns	Opinionated combinations of multiple resources (e.g., ApplicationLoadBalancedFargateService)

Stacks

A stack in CDK corresponds to a CloudFormation stack. You define a stack as a class:

import * as cdk from 'aws-cdk-lib';
import * as s3 from 'aws-cdk-lib/aws-s3';

export class MyAppStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
    super(scope, id, props);

    new s3.Bucket(this, 'MyBucket', {
      versioned: true,
      removalPolicy: cdk.RemovalPolicy.DESTROY,
      autoDeleteObjects: true,
    });
  }
}

Apps

An app is the root construct. It can contain multiple stacks:

const app = new cdk.App();

new MyAppStack(app, 'DevStack', {
  env: { region: 'eu-west-2' },
});

new MyAppStack(app, 'ProdStack', {
  env: { region: 'us-east-1' },
});

app.synth();

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Getting Started with CDK

Installation

npm install -g aws-cdk
cdk --version

Bootstrapping

Before you can deploy CDK apps, you must bootstrap your AWS account and region. This creates an S3 bucket and IAM roles that the CDK uses:

cdk bootstrap aws://123456789012/eu-west-2

Creating a New Project

mkdir my-cdk-app && cd my-cdk-app
cdk init app --language typescript

This generates a project structure with:

• lib/ — your stack definitions
• bin/ — the app entry point
• test/ — unit tests
• cdk.json — CDK configuration

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CDK vs CloudFormation YAML

Here is the same infrastructure defined in both CDK (TypeScript) and CloudFormation YAML: