5 AWS CDK Best Practices for Scalable Infrastructure

The AWS Cloud Development Kit (CDK) has revolutionized Infrastructure as Code (IaC) by allowing developers to define cloud resources using familiar programming languages. But as your applications grow, so does the complexity of your CDK code. Simply defining resources in your main stack file isn't enough.

Here are five essential best practices to help you write clean, scalable, and maintainable CDK applications.

1. Use Custom Constructs for Reusability

Don't repeat yourself! If you find you're defining the same group of resources over and over (like a Lambda function with an API Gateway endpoint and a DynamoDB table), encapsulate them into a custom Construct.

Before: Repetitive code in a stack

// MyStack.ts
// Service A
const serviceALambda = new lambda.Function(...);
const serviceAApi = new apigw.LambdaRestApi(this, 'ServiceAEndpoint', { handler: serviceALambda });

// Service B (very similar)
const serviceBLambda = new lambda.Function(...);
const serviceBApi = new apigw.LambdaRestApi(this, 'ServiceBEndpoint', { handler: serviceBLambda });

After: A reusable Construct

// lib/api-service-construct.ts
export class ApiService extends Construct {
  constructor(scope: Construct, id: string, props: ApiServiceProps) {
    super(scope, id);
    const lambdaFunction = new lambda.Function(this, 'MyFunction', ...);
    new apigw.LambdaRestApi(this, 'MyEndpoint', { handler: lambdaFunction });
  }
}

// MyStack.ts
new ApiService(this, 'ServiceA', { ... });
new ApiService(this, 'ServiceB', { ... });

This makes your stacks cleaner and ensures consistency across your services.

2. Separate Stacks by Environment and Lifecycle

Avoid creating a single, monolithic stack for your entire application. Instead, split your resources into multiple stacks based on their lifecycle and environment.

• Environment Stacks: Create different stacks for dev, staging, and prod. Use a configuration file or context variables to pass environment-specific settings (like VPC IDs or domain names).
• Lifecycle Stacks: Group resources that change together. For example, have a DatabaseStack for your persistent data stores and a separate ApplicationStack for your compute and API layers. This isolates changes and reduces the "blast radius" of a failed deployment.

// bin/my-app.ts
const app = new cdk.App();

// A persistent, foundational stack
const networkStack = new NetworkStack(app, 'NetworkStack-Prod');

// The application stack, which might be updated more frequently
new ApplicationStack(app, 'AppStack-Prod', { vpc: networkStack.vpc });

3. Use cdk-nag for Security and Compliance

cdk-nag is a fantastic tool that checks your CDK application for compliance with common security best practices. It can automatically flag issues like unencrypted S3 buckets, overly permissive IAM roles, or public database instances.

Integrating it is simple:

// bin/my-app.ts
import { App, Aspects } from 'aws-cdk-lib';
import { AwsSolutionsChecks } from 'cdk-nag';

const app = new App();
// ... define your stacks

// Add the cdk-nag Aspect to the entire app
Aspects.of(app).add(new AwsSolutionsChecks({ verbose: true }));

Running cdk synth will now produce warnings or errors for any non-compliant resources, helping you build a more secure infrastructure from the start.

4. Parameterize Your Stacks with Props

Hardcoding values like domain names, memory sizes, or VPC IDs directly in your constructs or stacks makes them inflexible. Always pass configuration down through props interfaces.

Before: Hardcoded values

export class MyStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);
    new lambda.Function(this, 'MyFunc', {
      memorySize: 1024, // Hardcoded
      // ...
    });
  }
}

After: Using a props interface

interface MyStackProps extends cdk.StackProps {
  lambdaMemorySize: number;
}

export class MyStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props: MyStackProps) {
    super(scope, id, props);
    new lambda.Function(this, 'MyFunc', {
      memorySize: props.lambdaMemorySize, // From props
      // ...
    });
  }
}

This makes your stacks reusable and testable, as you can easily instantiate them with different configurations.

5. Leverage Logical IDs for Predictable Naming

By default, the CDK generates unique, hash-based physical names for resources to prevent naming conflicts. However, sometimes you need a predictable name. Instead of hardcoding a bucketName, use the CDK's logical ID system and exports/imports.

If you must have a specific name, it's better to pass it in from a configuration context, but be aware that this resource can't be replaced without manual intervention. For most resources, it's better to let the CDK manage the physical name and reference the resource through its logical ID.

Example: Referencing an S3 bucket

// In one stack
const bucket = new s3.Bucket(this, 'MyDataBucket');
new cdk.CfnOutput(this, 'BucketNameExport', {
  value: bucket.bucketName,
  exportName: 'MyDataBucketName',
});

// In another stack
const bucketName = cdk.Fn.importValue('MyDataBucketName');
const bucket = s3.Bucket.fromBucketName(this, 'ImportedBucket', bucketName);

By following these best practices, you can build AWS CDK applications that are not only powerful but also robust, scalable, and easy to maintain as your project grows.