What is Infrastructure as Code?

Before the cloud, infrastructure was physical — you ordered servers, racked them, cabled them, and configured them manually. With virtualisation and the cloud came a new problem: managing hundreds of virtual machines, networks, and services through web consoles is slow, inconsistent, and impossible to audit or reproduce.

The Problem with Manual Infrastructure

• Slow: Every change requires human intervention through a UI or SSH session.
• Inconsistent: "Click-ops" produces snowflake servers — each slightly different.
• Not reproducible: Can you recreate your entire infrastructure in a new region in an hour? Without IaC, probably not.
• No audit trail: Who changed that security group? When? There's no git history for manual changes.
• Configuration drift: Over time, manual changes accumulate and dev, staging, and prod diverge unpredictably.

What is Infrastructure as Code?

Infrastructure as Code (IaC) is the practice of defining and managing infrastructure resources — servers, networks, databases, load balancers — through machine-readable configuration files, just like application code.

These files can be:

• Stored in version control (Git)
• Reviewed via pull requests
• Tested in CI pipelines
• Applied consistently across multiple environments
• Rolled back to a previous state

Declarative vs Imperative IaC

Terraform is declarative. You write:

resource "aws_instance" "web" {
  ami           = "ami-0abcdef1234567890"
  instance_type = "t3.micro"
}

Terraform determines whether to create, modify, or destroy the instance based on the current state of your infrastructure.

Key Benefits of IaC

• Repeatability: Deploy the same infrastructure to dev, staging, and prod with confidence they match.
• Speed: Provision a full environment in minutes, not days.
• Documentation: The code is the documentation. No more "tribal knowledge."
• Cost visibility: Count resources in code before applying.
• Disaster recovery: Recreate your entire infrastructure from code if needed.
• Collaboration: Teams can review infrastructure changes like they review feature code.

The IaC Ecosystem

Terraform has become the dominant IaC tool for provisioning cloud resources across multiple providers. Next: a closer look at Terraform and how it compares to the alternatives.