Terraform at Scale: Managing Multi-Environment GCP Infrastructure

Infrastructure as Code stopped being optional years ago. If you're still clicking through the GCP console to provision resources, you're creating debt that compounds with every deployment.

At its core, Terraform gives you a declarative way to describe infrastructure. You define what you want, and Terraform figures out how to get there. But the gap between a simple main.tf and a production-grade multi-environment setup is enormous.

The first decision that matters is module design. I structure Terraform modules around logical service boundaries, not resource types. A 'service' module might include a Cloud Run service, its IAM bindings, a Cloud SQL database, and the networking rules that connect them. This mirrors how teams think about their systems.

State management is where most teams stumble. Remote state in a GCS bucket with state locking is table stakes. But you also need to think about state isolation. Each environment, dev, staging, production, should have its own state file. I use Terraform workspaces for simple setups and completely separate backend configurations for larger ones.

Variables and tfvars files handle environment-specific configuration. A common pattern: define a variables.tf with sensible defaults, then override per environment with terraform.tfvars files. This keeps the module generic while allowing each environment to diverge where needed.

The CI/CD integration is critical. I use GitHub Actions with Workload Identity Federation to authenticate to GCP without service account keys. The pipeline runs terraform plan on every PR, posts the plan as a comment, and only applies on merge to main. This gives the team visibility into infrastructure changes before they happen.

One pattern I've found invaluable is tagging every resource with a managed_by = terraform label. This makes it trivially easy to identify resources that were created manually and need to be imported or removed.

The biggest lesson: treat your Terraform code with the same rigor as application code. Code review, testing with terraform validate and tflint, and documentation are not optional.