The IaC landscape split into two philosophies about a decade ago and hasn't fully resolved the argument since. On one side: declarative configuration languages designed specifically for infrastructure (Terraform HCL, CloudFormation YAML, Bicep). On the other: general-purpose programming languages brought to infrastructure (AWS CDK, Pulumi). Both approaches have won in production at major organizations. Neither is clearly superior.
This comparison covers Terraform, AWS CDK, and Pulumi in depth — how they work, where they excel, where they struggle, and which makes sense for different team situations. It isn't a beginner introduction to any of these tools; if you're choosing between them for a real project, this assumes you've at least skimmed each one.
The core philosophical difference
Terraform's HCL is a purpose-built configuration language. It's not Turing-complete (no arbitrary loops, no recursion, limited conditionals). This is by design: HashiCorp's position is that infrastructure definitions should be readable, predictable, and safe to generate tooling around. When you read a .tf file, you can understand what it creates without executing anything.
CDK and Pulumi take the opposite position: the limitations of configuration languages are a tax on productive engineers. Why invent a domain-specific language when TypeScript already exists? Real programming languages have proper abstractions, test frameworks, package managers, IDE support, and a billion engineers who already know them. Infrastructure should be no different from application code.
