Build Phase

The Build phase organizes and structures IaC into a repository model that enforces consistency.

Core Concepts

• Repository Structure: Organized into modules/, solutions/, and deployments/ directories
• Solutions enforce consistency across services by explicitly defining constraints

Example Repository Structure

your-idlc-repo/
├── modules/
│   ├── s3/
│   │   └── bucket/
│   │       ├── main.tf
│   │       ├── variables.tf
│   │       ├── outputs.tf
│   │       └── versions.tf
│   ├── rds/
│   │   ├── postgres-database/
│   │   ├── parameter-group/
│   │   └── alarms/
│   └── eks/
│       ├── cluster/
│       ├── karpenter/
│       └── irsa/
├── solutions/
│   ├── my-app/
│   │   ├── main.tf          # Composes modules
│   │   ├── variables.tf     # Only what varies
│   │   └── outputs.tf
│   └── my-database/
│       ├── main.tf
│       └── variables.tf
└── deployments/
    ├── region-1/
    │   ├── stage/
    │   │   └── my-app/
    │   │       └── terragrunt.hcl
    │   └── production/
    │       ├── root.hcl
    │       └── my-app/
    │           └── terragrunt.hcl
    └── region-2/
        └── production/
            └── my-app/
                └── terragrunt.hcl

Module File Convention

Every module should contain:

File	Purpose
main.tf	Resource definitions
variables.tf	Input variables with validation
outputs.tf	Output values
versions.tf	Provider and Terraform version constraints
README.md	Auto-generated by terraform-docs
CHANGELOG.md	Auto-generated by release-please

Documentation

Documentation is generated from code comments using terraform-docs and included in the module’s README.md. This ensures documentation is always up-to-date with the code. But is highly recommended to add a custom block into README.md with usage examples, architectural decisions, and any non-obvious details that code comments can’t capture.

Our custom documentation block (not generated by terraform-docs)
<!-- BEGIN_TF_DOCS -->
Auto gererated documentation from terraform-docs will be injected here
<!-- END_TF_DOCS -->

Best Practices

• Use clear, consistent naming for directories and modules
• Enforce non-configurable defaults in solutions (security, policies)
• Keep modules focused on a single responsibility
• Use versions.tf to pin provider versions

Build is about structure and enforcement. A well-organized repository makes the Code and Deploy phases significantly easier.