Infrastructure as Code with Terraform: Managing Cloud at Scale

Infrastructure as Code (IaC) has become an essential practice for any organization managing cloud resources. Writing infrastructure definitions in declarative configuration files rather than clicking through console UIs provides version control, peer review, automated testing, and repeatable deployments. Terraform, by HashiCorp, remains the most widely adopted IaC tool due to its provider ecosystem and cloud-agnostic design. At Nexis Limited, Terraform is a core part of our cloud engineering practice.

Why Terraform Over Alternatives

While AWS CloudFormation and Azure Resource Manager templates serve their respective clouds well, Terraform excels in multi-cloud environments and offers a consistent workflow regardless of the target provider. Its declarative HCL syntax is readable and expressive. The plan-apply workflow gives teams a clear preview of changes before they are executed, reducing the risk of unintended modifications. Terraform also supports a vast ecosystem of providers beyond major cloud platforms, including DNS, monitoring, database, and SaaS service providers.

Module Design and Reusability

Terraform modules are the building blocks of scalable infrastructure code. A well-designed module encapsulates a logical unit of infrastructure, such as a VPC with subnets and security groups, or an ECS service with load balancer and auto-scaling. Modules should accept input variables for customization and expose output values that other modules can reference. Follow the principle of least privilege in module design: expose only the configuration knobs that consumers genuinely need.

We maintain a private module registry with battle-tested modules for common patterns: VPC networking, RDS databases, ECS/Fargate services, S3 and CloudFront distributions, and IAM role management. These modules encode organizational best practices and compliance requirements, ensuring that every new project starts with a secure, well-architected foundation.

Module Versioning and Testing

Version your modules using semantic versioning and pin module sources to specific versions in consumer code. Never reference modules by branch or latest tag in production configurations. Test modules using Terratest or the built-in terraform test framework. Automated tests should validate that modules create the expected resources with correct configurations and that destroy operations clean up fully.

State Management Best Practices

Terraform state is the single source of truth for your infrastructure. Remote state backends like S3 with DynamoDB locking or Terraform Cloud are mandatory for team environments. Local state files are acceptable only for individual experimentation. Enable state encryption at rest and restrict access to state files, as they often contain sensitive information like database passwords and API keys.

State splitting is crucial at scale. Rather than managing your entire infrastructure in a single state file, split state by environment, region, or service boundary. This reduces blast radius, improves plan and apply performance, and enables independent team workflows. Use data sources and remote state references to share information between state files.

Team Workflow and Collaboration

Integrate Terraform into your CI/CD pipeline with automated plan generation on pull requests. Developers should see the exact infrastructure changes their code will produce before merging. Apply operations should be restricted to the CI system or a limited set of operators to maintain an audit trail. Terraform Cloud and Spacelift offer managed workflow platforms with policy enforcement, cost estimation, and drift detection.

Handling Drift and Import

Infrastructure drift occurs when manual changes are made outside of Terraform. Regular drift detection using terraform plan in a scheduled pipeline catches drift early. When you need to bring existing resources under Terraform management, use the terraform import command or write import blocks in your configuration. Document imported resources thoroughly, as their initial configuration may not match your module defaults.

Infrastructure as Code is not just a technical practice but a cultural shift towards treating infrastructure with the same rigor as application code. Our teams at Nexis Limited help organizations adopt Terraform effectively, from initial setup to enterprise-scale governance. Learn more about our services, or contact us to start your IaC journey.