Infrastructure as Code (IaC) with AWS CloudFormation and AWS CDK

Automate, Standardize, and Scale Your Cloud Infrastructure

Managing cloud resources manually is inefficient and error-prone—especially at scale. With Infrastructure as Code (IaC), you can define, provision, and update AWS infrastructure using code, making deployments repeatable, testable, and version-controlled.

This chapter dives into:

• CloudFormation (YAML/JSON templates)
• AWS CDK (Cloud Development Kit using TypeScript, Python, etc.)
• Real-world use cases, best practices, and CLI commands

🔍 What is Infrastructure as Code (IaC)?

IaC is the practice of managing and provisioning infrastructure through machine-readable configuration files, rather than through physical hardware or manual configuration.

Benefits of IaC:

• ✅ Automation & Repeatability
• ✅ Version control via Git
• ✅ Easy collaboration in teams
• ✅ Fast provisioning of complete environments
• ✅ Lower risk of human error

🧱 AWS IaC Options Comparison

📌 This chapter focuses on CloudFormation and CDK, both native to AWS.

Section 1: AWS CloudFormation – Declarative IaC

🔍 What is CloudFormation?

AWS CloudFormation is a service that enables you to describe your AWS infrastructure using YAML or JSON templates.

You can deploy:

• EC2 instances
• S3 buckets
• VPCs, IAM roles, Lambda functions, RDS databases, etc.
• Entire architectures with dependencies, conditions, and outputs

📑 CloudFormation Template Structure

AWSTemplateFormatVersion: '2010-09-09'
Description: Simple S3 Bucket
Resources:
  MyS3Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-scriptbuzz-bucket

AWSTemplateFormatVersion: '2010-09-09'
Description: Simple S3 Bucket
Resources:
  MyS3Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: my-scriptbuzz-bucket

✅ Key Sections:

Deploying a CloudFormation Stack (CLI)

aws cloudformation create-stack \
  --stack-name my-s3-stack \
  --template-body file://template.yaml \
  --capabilities CAPABILITY_NAMED_IAM

aws cloudformation create-stack \
  --stack-name my-s3-stack \
  --template-body file://template.yaml \
  --capabilities CAPABILITY_NAMED_IAM

🧠 Use CAPABILITY_NAMED_IAM when IAM roles or policies are included in the template.

🔄 Updating a Stack

• Change your YAML template
• Run:

aws cloudformation update-stack \
  --stack-name my-s3-stack \
  --template-body file://template.yaml

aws cloudformation update-stack \
  --stack-name my-s3-stack \
  --template-body file://template.yaml

CloudFormation automatically handles diffing, replacement, or in-place updates.

Real-World Use Case

Multi-Tier Web App Deployment

Resources:
  WebServer:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: ami-0abcdef1234567890
      SecurityGroups:
        - Ref: WebServerSG

  WebServerSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow HTTP
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0

Resources:
  WebServer:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: ami-0abcdef1234567890
      SecurityGroups:
        - Ref: WebServerSG

  WebServerSG:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Allow HTTP
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 80
          ToPort: 80
          CidrIp: 0.0.0.0/0

💡 Use nested stacks for modularity (VPC, EC2, RDS as separate templates).

Best Practices for CloudFormation

• Use YAML over JSON for readability
• Keep templates modular and reusable
• Use Outputs and Exports to share values between stacks
• Parameterize for environment-specific values (e.g., Env=dev)
• Use change sets to preview updates before applying
• Version templates in Git

Section 2: AWS CDK – Programmatic IaC with Familiar Languages

🔍 What is AWS CDK?

AWS Cloud Development Kit (CDK) allows you to define AWS infrastructure using real programming languages:

• TypeScript (recommended)
• Python
• Java
• Go
• C#

The CDK compiles your code into a CloudFormation template, which is then deployed.

CDK Workflow

1. Write code using CDK constructs
2. cdk synth → generates CloudFormation template
3. cdk deploy → creates/updates stack
4. Infrastructure is live on AWS

🔧 Example CDK App (TypeScript)

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

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

    new Bucket(this, 'MyBucket', {
      versioned: true,
      bucketName: 'my-scriptbuzz-cdk-bucket'
    });
  }
}

const app = new cdk.App();
new MyStack(app, 'ScriptBuzzStack');

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

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

    new Bucket(this, 'MyBucket', {
      versioned: true,
      bucketName: 'my-scriptbuzz-cdk-bucket'
    });
  }
}

const app = new cdk.App();
new MyStack(app, 'ScriptBuzzStack');

CDK CLI Commands

cdk init app --language typescript
npm install aws-cdk-lib constructs
cdk synth        # Generate CloudFormation template
cdk deploy       # Deploy stack to AWS
cdk destroy      # Delete stack

cdk init app --language typescript
npm install aws-cdk-lib constructs
cdk synth        # Generate CloudFormation template
cdk deploy       # Deploy stack to AWS
cdk destroy      # Delete stack

🔁 CDK Constructs & Reusability

CDK uses constructs as building blocks.

• Level 1 (L1): direct CloudFormation mappings
• Level 2 (L2): opinionated, simplified versions
• Level 3 (L3): high-level reusable patterns

✅ You can publish your own CDK packages and reuse them across teams.

CDK Best Practices

• Use context values for environment-specific customization
• Store secrets in SSM Parameter Store or Secrets Manager
• Use constructs for encapsulation
• Use Git for versioning + CI/CD integration
• Combine CDK with CodePipeline for continuous deployment

Summary: CloudFormation vs CDK

✅ Real-World IaC Use Cases