Understanding IaC Tools: AWS CDK vs Terraform

Introduction

Infrastructure as Code (IaC) has rapidly emerged as a best practice for provisioning and managing cloud environments. By codifying infrastructure needs instead of manual processes, IaC enables greater efficiency, consistency and collaboration.

Benefits of IaC include:

• Increased speed and agility
• Improved reliability and recovery
• Enhanced collaboration across teams
• Documentation and version control
• Cost optimization

In fact, over 75% of organizations now utilize IaC in some form based on various industry surveys. And this adoption trajectory continues rising year-over-year.

However, several major IaC platform options exist across open source tools and cloud-provider managed services. Two popular choices deployed broadly include:

• HashiCorp Terraform: Open source, multi-cloud
• AWS Cloud Development Kit: AWS-native, CloudFormation-based

So how do you evaluate which approach best fits your needs? This guide compares the critical differences between Terraform vs AWS CDK to help inform your decision.

Multi-Cloud Support

A key strategic consideration is whether your infrastructure spans multiple cloud providers or lives exclusively in AWS.

Terraform natively integrates with 100+ infrastructure providers including AWS, Azure, GCP, Kubernetes, OpenStack and more. This facilitates a single point of automation and abstraction across many environments.

# Azure resource
resource "azurerm_resource_group" "mygroup" {
  name     = "my-resources"
  location = "West US 2"
}

# AWS resource 
resource "aws_s3_bucket" "data" {
  bucket = "my-tf-data-bucket"
  acl    = "private"
}

This simplifies orchestration for multi-cloud, hybrid cloud and edge computing patterns. Teams can stand up complex infrastructure without vendor lock-in.

In contrast, AWS CDK focuses specifically on AWS resource provisioning. While incredibly robust in capabilities, it does not address multi-cloud scenarios out of the box. Teams would need to adopt additional IaC tools to cover other providers.

Market Trends and Ecosystems

While both options boast healthy adoption, third-party data highlights some meaningful trends:

HashiCorp Terraform

• 500+ contributors to open source project
• ~3000+ modules in Terraform Registry
• Major cloud partners have joined the Terraform Partner Program
  • AWS, Azure, GCP
• ~100K+ Certified Terraform Associates globally

AWS CDK

• Growing share of AWS customers use AWS CDK over CloudFormation
• Accelerating third-party integrations like the CDK for Terraform
• Increasingly adopted by AWS partners around DevOps, security and more

So while AWS CDK momentum continues upwards, Terraform has captured significant mindshare as a flexible, cloud-agnostic automation platform.

Ease of Use

For individual developers ramping up, Terraform provides a more accessible initial learning curve. Its configuration syntax reads cleanly resembling a JSON-structured markup language.

resource "aws_instance" "web" {
  ami           = "ami-a1b2c3d4"
  instance_type = "t2.micro"
}

However, Terraform lacks native programming language capabilities for complex data transformations or mappings. Engineers often rely on lookup functions, null resources or external data sources to tackle one-off scenarios.

On the other hand, AWS CDK leverages the full power of TypeScript, Python and other programming languages. This unlocks advanced functionality like classes, custom types, validators and libraries. But getting started involves a steeper initial investment to become proficient.

Over time and at scale, AWS CDK can accelerate infrastructure development through robust language features. But Terraform may better suit tactical applications or fast prototyping needs.

Performance

When evaluating runtime characteristics:

• Terraform directly invokes infrastructure provider APIs as soon as you apply changes
• AWS CDK must synthesize executable AWS CloudFormation templates to implement your stacks

This extra step introduces a small amount of latency for AWS CDK around deployment speeds. In most applications, this delta should prove negligible. But when operating at massive scale, Terraform streamlines resource provisioning better through direct API interactions.

Modularity

Both platforms enable reusable modules or libraries to avoid "re-inventing the wheel":

Terraform Registries

Public/private registries house customizable infrastructure components. For example:

module "vpc" {
  source  = "terraform-aws-modules/vpc/aws"
  version = "3.19.0"
} 

AWS Construct Libraries

Developers publish infrastructure constructs like custom VPCs for others to integrate:

import { Vpc } from ‘@my-org/vpc-construct‘;

new Vpc(this, ‘MyVpc‘);

These reuse approaches boost productivity and encourage configuration consistency.

Policy Enforcement

Governing change in a secure fashion remains critically important as infrastructure scales up.

Both platforms integrate with AWS IAM for resource-level permission guardrails. Limit destructive actions through least privilege controls.

Additionally, Terraform offers Sentinel – an embedded policy-as-code framework. Enforce organizational standards around provisioning with reusable policy rules:

# Restrict expensive instance types
deny[msg] {
  input.type == "aws_instance"
  instance_type = input.instance_type
  prohibited_types = ["p3dn", "p4d"]
  contains(prohibited_types, instance_type)

  msg := "Instance type ${instance_type} prohibited"
}

These advanced capabilities help implement change governance, security and compliance requirements.

Making Your Choice

With an understanding of the key similarities and differences, how do you evaluate which IaC strategy to adopt?

Start by asking questions like:

• What cloud providers host your infrastructure today? Any plans for multi-cloud?
• What level of policy guardrails or governance is necessary?
• Will your developers know TypeScript/Python or prefer simpler YAML/JSON?
• What tradeoffs between initial ease-of-use vs long-term flexibility matter most?

Use these criteria to guide your decision between Terraform and AWS CDK:

Concern	Terraform	AWS CDK
Multi-Cloud Support	Yes	AWS-only
Learning Curve	Simpler	Steeper
Performance	Faster	Synthesis overhead
Policy Enforcement	Sentinel	IAM only

Beyond the technology, also factor in impacts to people and process. Re-skilling developers takes time. And toolchain integrations may influence the roadmap.

Ultimately both Terraform and AWS CDK offer robust infrastructure automation capabilities. Let your environmental context guide you to the best choice, potentially utilizing both tools in tandem.

Summary

I hope this breakdown of Terraform vs AWS CDK proved helpful. Building cloud-based systems is challenging enough without having to evaluate technical minutiae across platforms.

Leverage the strengths of these IaC solutions to empower your productivity over infrastructure drudgery. Let complexity be the boilerplate while your team focuses innovation on application logic and user experiences.

The future lies with organizations who harness cloud velocity securely, reliably and cost-effectively through Infrastructure as Code. Bring clarity to that vision by making an informed choice on your approach.

Now go unlock innovation for your customers without technological barriers or distractions. The power lies at your fingertips – limited only by imagination, backed by cloud scale.