Matthias Schenk

Senior Software Engineer/Craftsman experienced in Java/Kotlin

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In my last post I talked about the KISS principle and its importance for software development. Today another acronym waits for explanation.

In the world of software development, there’s a constant push to innovate, improve, and stay ahead of the curve. Developers are often tempted to anticipate future needs, adding features or capabilities that might be required down the line. However, this well-meaning approach can lead to bloated codebases, wasted effort, and slower development cycles. This is where the YAGNI principle comes into play.

What is YAGNI?

YAGNI stands for "You Aren’t Gonna Need It." It’s a principle of extreme programming (XP) that advises developers to avoid adding functionality unless it’s absolutely necessary. The core idea is simple: don’t build features until they’re required by the user or the project. The same is true for technical complexity: Don’t implement technical functionality like e.g. distributed transactions, messaging solutions with Kafka, that is not necessary now.

At first glance, this might seem counterintuitive. Isn’t it a good idea to prepare for future needs? While proactive planning is essential in software development, YAGNI emphasizes the importance of focusing on what’s needed right now. By doing so, developers can create more efficient, maintainable, and agile code.

Why YAGNI Matters

  • Reduced Complexity Every new feature or piece of code adds complexity to a project. By only building what’s needed, you keep your codebase clean, understandable, and easier to maintain. Complex code is harder to debug, test, and extend, leading to potential issues in the long run.

  • Faster Development When you stick to the essentials, you speed up the development process. You’re not spending time building, testing, and maintaining features that might never be used. This allows you to deliver the core functionality faster and iterate based on real user feedback.

  • Improved Focus YAGNI helps teams focus on delivering value. It ensures that development efforts are aligned with current project goals, rather than being distracted by speculative features. This focus leads to better product quality and user satisfaction. This is one of my favorite arguments because having less things to care about in the development phase increases the quality of the results.

  • Avoiding Waste Time and resources are precious in any development project. By following YAGNI, you minimize waste by only working on what’s truly necessary. This aligns with the lean development philosophy, which aims to eliminate anything that doesn’t add value to the customer.

Applying YAGNI in Practice

  • Start with the Minimum Viable Product (MVP) When beginning a project, focus on building the MVP—the simplest version of your product that meets the core requirements. This approach aligns perfectly with YAGNI, ensuring that you’re only developing what’s necessary to validate your product idea.

  • Refactor Regularly As your project evolves, you might find that certain features become necessary. In these cases, refactor your code to include the new functionality, but do so in a way that maintains simplicity and avoids unnecessary complexity.

  • Rely on Real User Feedback Instead of guessing what users might need in the future, let their feedback guide your development process. This not only ensures that you’re building what users actually want but also helps you prioritize the most important features.

  • Use Feature Toggles If you’re unsure whether a feature will be needed, consider using feature toggles. This allows you to add the functionality but keep it disabled until it’s confirmed to be necessary. It’s a way to experiment without fully committing to unnecessary code.

Common Misconceptions About YAGNI

YAGNI Discourages Planning: Some developers misunderstand YAGNI as an argument against planning for the future. However, YAGNI doesn’t reject planning; it simply advises against implementing features prematurely. Proper planning should still consider future needs, but implementation should wait until those needs are certain.

YAGNI Leads to Short-Sightedness: Critics argue that YAGNI might cause developers to miss the bigger picture. In reality, YAGNI promotes a more iterative approach to development, where the software evolves based on real-world use rather than speculative assumptions. This can lead to a more robust and user-centered product.

Conclusion

The YAGNI principle is a powerful tool in developers tool box seeking to build efficient, maintainable, and user-focused software. By resisting the urge to over-engineer or anticipate future needs prematurely, teams can avoid unnecessary complexity, reduce waste, and deliver higher-quality products. In a fast-paced development environment, YAGNI helps keep the focus on what truly matters—delivering value to the user here and now.

Whether you’re working on a small project or a large-scale application, keeping YAGNI in mind can lead to better decisions, faster development cycles, and ultimately, a more successful product. Remember, sometimes the best feature is the one you didn’t build.

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