IaC definition
Infrastructure as Code (IaC) is the practice of defining and managing cloud and data center infrastructure, such as networks, servers, databases and permissions, through machine-readable configuration files instead of manual setup. Tools like Terraform, AWS CloudFormation and Pulumi read these files and create or update resources automatically, making environments repeatable, reviewable and version-controlled.
How does Infrastructure as Code work?
Most IaC tools are declarative: you describe the desired end state, such as a private network with three subnets, a PostgreSQL database and an IAM role, and the tool works out how to get there. Terraform, for example, compares your configuration with its record of existing resources, shows a plan listing what it will create, change or destroy, and applies that plan through the cloud provider's APIs once you approve it.
Worked example: a team defines its network, database, container cluster and permissions as reusable modules. The same modules create staging and production with different sizes and settings, so the two environments stay consistent. A new region or a disaster recovery copy becomes a configuration change and a pipeline run rather than weeks of manual console work.
Popular IaC tools
- Terraform and OpenTofu: multi-cloud tools using HCL; OpenTofu is the open-source fork created after Terraform's license change.
- AWS CloudFormation and AWS CDK: native AWS templates, with CDK using TypeScript, Python and other languages.
- Azure Bicep and ARM templates: native Azure definitions.
- Pulumi: infrastructure in general-purpose languages such as TypeScript, Python and Go.
- Crossplane: manages cloud resources through Kubernetes APIs.
- Ansible: configuration management that can also provision resources.
Benefits of Infrastructure as Code
IaC brings software engineering habits to infrastructure. Every change goes through version control and code review, so there is an audit trail of who changed what and why. Environments can be recreated reliably, which turns disaster recovery from a document into a tested procedure. Consistency between development, staging and production removes a whole class of "works in staging" bugs, and the code itself documents how the system is built.
IaC best practices
Run IaC through a pipeline: plan automatically on every pull request so reviewers see the exact changes, and apply only after merge. Store state remotely with locking so two people cannot apply at once, and never edit resources manually in the console, since manual changes create drift that the next run may overwrite.
- Build small, reusable modules with clear inputs and outputs.
- Keep secrets out of code, using a secrets manager or vault.
- Scan configurations with policy tools such as Checkov, Trivy or Open Policy Agent.
- Detect drift on a schedule and alert on differences.
- Pin provider and module versions and upgrade deliberately.
- Tag resources automatically through shared module defaults.
IaC vs configuration management
Provisioning tools such as Terraform create infrastructure: networks, servers, databases and permissions. Configuration management tools such as Ansible, Chef and Puppet configure what runs on servers, such as packages, files and services. With containers and managed services, much of the configuration work has moved into images and platforms, so many teams now use Terraform or a similar tool for provisioning and containers for everything inside. Nexzem delivers every cloud environment it builds as IaC, handed over in the client's own repository.