Architecture as Code (AAC): Building Better Systems Through Code-Driven Architecture

As software systems grow in complexity, ensuring that architecture aligns closely with implementation is becoming more critical than ever. In traditional approaches, architectural diagrams and documents are often maintained separately from the codebase, leading to discrepancies between design intentions and actual implementations. Enter Architecture as Code (AAC), a concept that helps bridge this gap by treating architecture documentation as part of the codebase itself. In this post, we’ll explore why and how to approach architecture this way, particularly in the context of modern software systems.

What is Architecture as Code (AAC)?

Architecture as Code means expressing your architecture through code, treating it just like any other part of your software system. Instead of having a separate set of diagrams and documents, you write your architectural descriptions as executable code that can be checked into version control and maintained alongside your product code. This enables a continuous feedback loop, where the architecture evolves with the code and vice versa.

In AAC, architectural decisions aren’t just written in static documents; they are embedded in your codebase, versioned, and tested just like functional code. The architecture isn’t something that is only understood by architects; it’s something that all developers can interact with, understand, and evolve.

Why Architecture as Code?

There are several reasons why shifting to an AAC approach is beneficial, especially in modern development environments:

1. Consistency Across Teams: When your architecture is part of the codebase, it becomes a shared resource that all developers and architects can easily access. This consistency ensures that everyone is on the same page, and that architectural decisions are visible to anyone working on the code.
2. Automatic Validation and Testing: By integrating architecture into your CI/CD pipeline, you can continuously validate that the architecture aligns with the actual implementation. For example, tools like Structurizr allow you to create architecture diagrams from your codebase, enabling automatic validation of structure and design.
3. Maintainability: As your system evolves, so should your architecture. With AAC, keeping your architecture up-to-date becomes much easier since any changes to the codebase naturally prompt changes to architectural documentation. There’s no need to worry about outdated documents or diagrams falling out of sync.
4. Improved Collaboration: Architects, developers, and ops teams often work in silos. AAC helps foster collaboration because architectural decisions are now code artifacts. Developers can participate in architectural discussions, propose changes, and review updates directly in the code repository.
5. Documentation as First-Class Citizen: By treating architecture as part of the development process, architecture documentation no longer feels like a second-class citizen. It becomes integrated into the flow of the project, with clear ownership and responsibility from the same team that owns the code.

How to Implement Architecture as Code

Implementing AAC involves a few key steps, which I’ll outline below. But first, let’s talk about the tools that make it easier to embrace this approach.

Key Tools for AAC

1. Structurizr: A key tool in the AAC ecosystem, Structurizr uses the C4 model to describe software architecture through code. It allows you to define your architecture using a domain-specific language (DSL), and from that DSL, it generates live diagrams that reflect the current state of your system.
2. PlantUML: A widely used tool for creating diagrams from code. PlantUML can be integrated into build processes, enabling automatic updates of architectural diagrams whenever your system’s structure changes.
3. Model-Driven Development Tools: Tools like Sparx Systems Enterprise Architect or Archi help in the model-driven approach, but many of them now offer ways to integrate with codebases or work alongside version control systems.
4. Graph Databases: Graph databases like Neo4j can help map the relationships between your components. These tools provide visualisation options to explore dependencies in the system architecture, giving you insight into how everything fits together.

Steps to Get Started

1. Choose a Framework: The first step in implementing AAC is to choose an appropriate framework for documenting your architecture. The C4 model is a great starting point because it provides a clear, scalable way to model your system from high-level contexts down to detailed component diagrams.
2. Define Your Architectural Views: Based on your needs, define the various views that reflect different perspectives of your system. This might include system context diagrams, container diagrams, component diagrams, and even detailed class or sequence diagrams, depending on the level of detail required.
3. Embed the Architecture in Code: Use a tool like Structurizr to define the architecture in code. These definitions should be stored in your version control system and treated as first-class citizens in the development process. Over time, as your system evolves, these architecture definitions should be updated to reflect the changes made in the code.
4. Automate and Integrate: Once you’ve set up your architecture-as-code framework, the next step is automation. Integrate tools like Structurizr into your CI/CD pipeline so that whenever a new version of your code is deployed, the corresponding architectural diagrams are automatically updated.
5. Collaboration and Governance: Finally, make sure that all stakeholders—developers, architects, and even product managers—are involved in the process. Architecture as code makes it easier to involve everyone in design discussions, ensuring that the architecture continues to evolve in line with your business and technical needs.

Conclusion

Architecture as Code is a powerful approach to software architecture that brings significant benefits in terms of consistency, maintainability, and collaboration. By embedding architectural decisions directly into the codebase, it ensures that the architecture evolves with the system and stays aligned with the development process. This approach is particularly beneficial in agile environments where frequent changes are the norm, and it offers a way for developers to take an active role in the architecture of the system they’re building.