Avoid Mistakes When Building a Large Infrastructure Project on Aws Using Terraform

Published on 19 Jan 2026 by Adam Lloyd-Jones

Building a large-scale infrastructure project on AWS with Terraform is a significant undertaking that requires a shift from manual “ClickOps” to a software engineering mindset. Here is a breakdown of the critical mistakes to avoid, production-grade best practices, and resources to guide you.

1. Mistakes to Avoid

Infrastructure as Code (IaC) is powerful, but it also allows you to “automatically break many machines at once” if not handled correctly.

Storing State in Version Control: Never store your Terraform state file (.tfstate) in Git. This leads to three major issues: manual error (forgetting to pull/push updates), lack of locking (two people applying changes simultaneously, leading to corruption), and secrets exposure (state files store all data, including database passwords, in plain text).
Out-of-Band Changes: Once a resource is managed by Terraform, you must never modify it manually via the AWS Console. Manual tweaks cause configuration drift, leading to “snowflake servers” that are impossible to replicate and causing valid Terraform plans to fail because the state file no longer matches reality.
The “Monolithic” Stack: Avoid defining your entire infrastructure in a single folder or state file. Large modules are slow to plan, risky to update, and difficult to review. A mistake in a small staging component could inadvertently destroy your production database.
Renaming without State Migration: Simply renaming a resource identifier in your code (e.g., changing resource "aws_instance" "app" to "web") will cause Terraform to delete the existing resource and create a new one. To rename without downtime, you must use the moved block or the terraform state mv command.
Neglecting Version Pinning: Failing to pin your Terraform and provider versions leads to “rug pulls” where a new release breaks your code unexpectedly. Always specify exact versions for the Terraform binary and a version range for providers.

2. Best Practices for Production

To run Terraform in production with confidence, you must build “bulkheads” into your architecture to contain failures.

Remote State with Locking and Encryption: Use a remote backend, such as Amazon S3, to store state. Pair this with a DynamoDB table for state locking to prevent race conditions and ensure only one person can apply changes at a time.
Environment Isolation via File Layout: Use separate folders for different environments (e.g., stage/, prod/) rather than just using workspaces. This makes it much clearer where changes are being applied and allows for different access permissions (e.g., limiting who can touch the prod/ folder).
Modularize Everything: Package your code into small, composable modules. Think of these as “blueprints” that can be reused across different environments. This reduces code duplication and allows you to test improvements in staging before promoting them to production.
Automated Testing: Infrastructure code without tests is effectively broken. Implement a testing pyramid:
- Unit/Integration Tests: Use Terratest (Go) or the Terraform Testing Framework (HCL) to deploy real infrastructure in a temporary sandbox, validate it, and tear it down.
- Static Analysis: Use TFLint to catch errors and Checkov or Trivy to scan for security misconfigurations (like open S3 buckets) before deployment.
Immutable Infrastructure Pattern: Favor replacing resources over updating them in place. Use the create_before_destroy lifecycle setting to ensure a new resource is healthy before the old one is terminated, enabling zero-downtime deployments.
Deploy from a CI Server: Never run terraform apply from your local laptop for production. Deployments should be triggered via CI/CD pipelines (e.g., GitHub Actions, Azure Pipelines) to ensure a consistent environment and a clear audit trail.

3. Resources Beyond Official Docs

While the official documentation is a necessary reference, there are several key books and tools for mastering production workflows:

Recommended Books:

*Terraform: Up & Running* (Yevgeniy Brikman): Focuses on real-world setting, reusability, and team workflows.
*Terraform in Depth* (Robert Hafner): Covers advanced implemented, provider development, and the OpenTofu fork.
*Infrastructure as Code* (Kief Morris): Essential for understanding the underlying principles of managing servers in the cloud.
*Terraform in Action* (Scott Winkler): Provides deeper technical insights into the engine.

Community Tools:

Terragrunt: A thin wrapper used to keep your backend configuration and CLI arguments DRY across multiple environments.
Atlantis: An open-source tool that runs terraform plan and apply directly from Git pull requests, facilitating better team collaboration.
Cloud-Nuke / AWS-Nuke: Tools used to periodically “nuke” or clean up orphaned resources in your sandbox/test accounts to prevent spiraling costs.
Tflint: A linter used specifically to catch provider-specific errors that standard validation might miss.

Adam Lloyd-Jones

Adam is a privacy-first SaaS builder, technical educator, and automation strategist. He leads modular infrastructure projects across AWS, Azure, and GCP, blending deep cloud expertise with ethical marketing and content strategy.

Avoid Mistakes When Building a Large Infrastructure Project on Aws Using Terraform

1. Mistakes to Avoid

2. Best Practices for Production

3. Resources Beyond Official Docs

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Adam Lloyd-Jones