Why Infrastructure as Code

Infrastructure as Code (IaC) manages cloud resources through configuration files rather than manual console clicks. This approach makes infrastructure reproducible, version-controlled, peer-reviewable, and testable — the same principles that make application code reliable. At Nexis Limited, Terraform manages all our cloud infrastructure across AWS and GCP.

Terraform Fundamentals

Terraform uses a declarative language (HCL) to define the desired state of infrastructure. You describe what you want — a VPC, subnets, load balancer, database — and Terraform calculates the steps needed to reach that state. The plan-apply workflow shows you exactly what will change before any modification is made.

Module Design

Modules are Terraform's primary mechanism for code reuse. A well-designed module encapsulates a logical group of resources — a Kubernetes cluster, a database with read replicas, or a complete network stack. Key practices:

  • Keep modules focused on one concern (networking, compute, storage).
  • Use input variables for configuration and output values for resource attributes needed by other modules.
  • Version modules and reference specific versions in root configurations.
  • Document inputs, outputs, and usage examples in the module's README.

State Management

Terraform state tracks the mapping between your configuration and real-world resources. For team environments, store state remotely in S3 with DynamoDB locking or GCS with built-in locking. Never commit state files to version control — they can contain sensitive information like database passwords.

Environment Management

We use Terraform workspaces combined with variable files for managing multiple environments (development, staging, production). Each environment uses the same Terraform modules but with different variable values for instance sizes, replica counts, and feature flags.

Common Patterns

  • VPC with public/private subnets: Internet-facing resources in public subnets, databases and application servers in private subnets, NAT gateway for outbound internet access.
  • EKS/GKE cluster: Managed Kubernetes cluster with node groups, IAM roles, and ingress controller.
  • RDS with read replicas: Primary database instance with automated backups, read replicas for query distribution, and parameter groups.
  • S3/GCS for static assets: Object storage buckets with CDN distribution, lifecycle policies, and access logging.

Security Best Practices

  • Use the principle of least privilege for IAM roles.
  • Never hardcode credentials in Terraform files — use environment variables or secret managers.
  • Enable encryption at rest for all storage resources.
  • Scan Terraform configurations with tools like checkov or tfsec for security misconfigurations.

Conclusion

Infrastructure as Code with Terraform transforms infrastructure management from a manual, error-prone process into a systematic, auditable practice. Start simple, modularize incrementally, and treat your infrastructure code with the same rigor as your application code.

Need help with cloud infrastructure? Our DevOps team designs and manages infrastructure for production SaaS products.