Applying the DRY (don't repeat yourself) principle to infrastructure-as-code

The DRY principle, which stands for “don’t repeat yourself,” is a well-established concept in software development that now plays an essential role in IaC, ensuring that configurations are efficient and streamlined. Without DRY, IaC quickly becomes bloated with redundant code, leading to configuration drift and excessive maintenance across environments. This technical debt, in turn, can spurn issues with security, scalability and cost management.

Gartner predicts that public cloud spending will reach nearly $675 billion this year, highlighting the increased complexity of managing cloud resources at scale. As IaC gains traction as a method for automating infrastructure provisioning, tools like Terraform have become essential for defining and automating cloud resources across environments. The risk of redundancy and inconsistency grows with the scale of these configurations. 

By applying DRY to IaC, IT teams can maintain clean, manageable configurations that prevent configuration drift and support scalability.

Common issues in IaC without DRY practices

When IaC isn’t informed by DRY principles, it often results in redundant configurations across environments, making maintenance a time-intensive and error-prone task. 

Redundant code leads to configuration drift, a prevalent issue where infrastructure gradually diverges from the desired state due to manual changes or uncoordinated updates, which results in added maintenance burden. Configuration drift and redundant code can impact cloud costs, especially when resources are scaled manually across cloud platforms like AWS and Google Cloud. 

Managing dependencies also becomes difficult without DRY. Interdependent infrastructure components across multiple configurations create bottlenecks that slow down updates and increase the risk of errors, complicating the deployment process.

Taking DRY further with Terragrunt

While DRY principles are essential for effective IaC, achieving them consistently requires tools designed for streamlined configuration management. This is where Terragrunt comes in, acting as a wrapper around Terraform to eliminate redundancies across environments. 

Terragrunt enables teams to centralize common configurations, avoid repetition, and manage dependencies efficiently. DevOps teams can thus define shared configurations once and apply them across multiple environments, helping to avoid configuration drift and manual errors.

For instance, organizations with multi-account setups can benefit from Terragrunt’s ability to manage backend configurations, IAM roles, and other environment-specific parameters from a single file, reducing the need for separate configuration files in each account. Terragrunt’s run-all command also allows updates to propagate across environments in parallel, minimizing operational friction. 

With Terragrunt, IT teams can manage dependencies, backend configurations, and environment-specific variables all from a central location. Following Terragrunt guidelines helps teams structure their configurations to maximize DRY principles, ensuring consistency across even the most complex infrastructures.

Applying DRY principles using Terraform modules

While Terragrunt centralizes configurations, Terraform modules provide a complementary method to achieve DRY in IaC by organizing code into reusable units. Modules allow teams to set up templates for infrastructure components, such as networking, storage, and IAM configurations, which can be applied universally across multiple environments.

For example, a Terraform module for managing VPC configurations can standardize network setups across environments. Changes to VPC security settings or IP configurations within the module propagate across development, staging, and production, ensuring consistent security standards without the need for multiple updates.

Modules also simplify dependency management. When infrastructure resources are grouped into modules, it’s easier to maintain their dependencies and update configurations without requiring adjustments across separate configuration files. By modularizing core infrastructure resources, Terraform allows applications to scale faster and improve maintainability while keeping IaC clean and organized.

Best practices for DRY in IaC

Consolidating shared configurations into centralized files and integrating them into CI/CD pipelines ensures DRY compliance by minimizing manual changes and automating validation across environments. This ensures that every instance remains consistent with core configurations. Centralizing configurations also makes compliance checks easier, simplifying the process of tracking and auditing infrastructure changes across multi-account setups.

Terraform modules play a crucial role in making IaC scalable and DRY-compliant. By organizing infrastructure resources into reusable modules such as networking, security policies, and IAM configurations, teams can replicate reliable, tested setups across environments without duplicating code. Modular patterns not only save time but also reduce the risk of errors, as changes to a single module can propagate across all environments using that module.

Integrating IaC configurations into CI/CD pipelines with automated testing is critical for maintaining DRY standards. Each change can be automatically validated to ensure it aligns with DRY principles and adheres to security and compliance standards before deployment. This setup minimizes the risk of manual errors, particularly in complex, multi-environment infrastructures, where human oversight can result in configuration drift.

Maintaining version control on IaC configurations provides clear traceability, helping teams manage changes, troubleshoot issues, and roll back to previous configurations if necessary. Tools like GitHub and GitLab enable teams to track IaC changes across environments, ensuring consistency while offering visibility into who made changes and why, mitigating unintended divergences across environments.

Dependency management is crucial in IaC, where different infrastructure components—such as databases, load balancers, and application servers—rely on each other for proper functionality. Centralizing dependencies within modules ensures consistent configurations and minimizes redundant code.

When following DRY principles, it’s best to avoid environment-specific overrides unless absolutely necessary. Overuse of overrides can lead to configuration drift and negate the benefits of centralized configurations. Instead, use environment-specific variables only for critical differences, such as region or instance type, while keeping core configurations consistent. Tools like Terragrunt allow selective overrides without duplicating entire configurations, maintaining a clean DRY structure even when some customization is needed.

As infrastructure requirements evolve, so should IaC configurations. Establishing a regular audit routine ensures that configurations stay DRY-compliant and optimized. These audits help identify redundant code, deprecated configurations, and unnecessary environment-specific overrides. Optimization routines can include refactoring modules to improve efficiency or adjusting configurations to meet new organizational requirements.

Takeaways

DRY principles in IaC are essential for reducing complexity, minimizing error rates, and supporting efficient multi-environment infrastructure management. Using Terragrunt to centralize configurations and Terraform modules for reusability, teams can build adaptable, resilient infrastructures that meet the demands of scaling businesses. Adopting DRY isn’t just a technical choice. It’s a strategic investment in sustainable infrastructure management that will support scalability, cost efficiency, and operational agility for years to come.