AWS CDK — Define Cloud Infrastructure Using Real Programming Languages

What it is

The AWS Cloud Development Kit (CDK) lets you define cloud infrastructure using familiar programming languages instead of YAML or JSON templates. Write TypeScript, Python, Java, Go, or C# code that describes your AWS resources, and CDK synthesizes it into CloudFormation templates and deploys them.

CDK provides high-level constructs that bundle multiple AWS resources with best-practice defaults. A single L2 construct can create a Lambda function with its IAM role, log group, and API Gateway integration.

How it saves time or tokens

CloudFormation YAML is verbose and error-prone. A Lambda function with API Gateway can take 100+ lines of YAML. The same setup in CDK takes 10 lines of TypeScript with sensible defaults for IAM, logging, and error handling.

For AI code generation, CDK's type-safe interfaces mean LLMs can produce correct infrastructure code with autocomplete-friendly APIs. TypeScript CDK code benefits from full type checking before deployment.

How to use

1. Install CDK and create a project:

npm install -g aws-cdk
cdk init app --language typescript

1. Define infrastructure in code:

import * as cdk from 'aws-cdk-lib';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as apigateway from 'aws-cdk-lib/aws-apigateway';

export class MyApiStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string) {
    super(scope, id);

    const fn = new lambda.Function(this, 'Handler', {
      runtime: lambda.Runtime.PYTHON_3_12,
      code: lambda.Code.fromAsset('lambda'),
      handler: 'index.handler',
    });

    new apigateway.LambdaRestApi(this, 'Api', { handler: fn });
  }
}

1. Deploy:

cdk deploy

1. CDK synthesizes CloudFormation, creates the stack, and provisions all resources.

Example

// CDK creates IAM role, log group, and API Gateway automatically
const fn = new lambda.Function(this, 'Processor', {
  runtime: lambda.Runtime.NODEJS_20_X,
  code: lambda.Code.fromAsset('src'),
  handler: 'processor.handler',
  timeout: cdk.Duration.seconds(30),
  memorySize: 256,
});

// Grant the function read access to an S3 bucket
bucket.grantRead(fn);

Related on TokRepo

• AI Tools for DevOps — Infrastructure-as-code and deployment tools
• AI Tools for Coding — AI-assisted infrastructure development

Common pitfalls

• Not running cdk diff before cdk deploy. Always review the change set to understand what resources will be created, modified, or destroyed.
• Using L1 constructs when L2 exists. L1 constructs are raw CloudFormation mappings. L2 constructs provide higher-level abstractions with best-practice defaults. Always check for L2 first.
• Ignoring CDK context and environment separation. Use cdk.json context and environment-specific stacks to manage dev, staging, and production deployments cleanly.
• Failing to review community discussions and changelogs before upgrading. Breaking changes in major versions can disrupt existing workflows. Pin versions in production and test upgrades in staging first.