What is maintainability? A basic overview

I once opened a codebase I inherited and found variable names like temp and x1 scattered throughout, as well as many functions with names like calcStuff that were over 300 lines long and had no comments. A simple feature request turned into almost five weeks of reverse engineering someone else’s thought process.

Unfortunately, this experience isn’t unique—many developers inherit unmaintainable codebases. This nightmare highlights why maintainability—the ease with which software can be understood, modified, and extended—is crucial for development teams.

In this article, you’ll gain an understanding of what maintainability means, why it matters, the key factors that influence it, best practices to improve it, and the common challenges teams face when trying to keep their code easy to update and scale.

In software development, change isn’t optional—it’s inevitable.

What is maintainability?

Maintainability is how easy it is to change, fix, or improve software as time goes on. In software development, change isn’t optional—it’s inevitable.

The Consortium for Information & Software Quality (CISQ) puts it formally: “Maintainability represents the degree of effectiveness and efficiency with which a product or system can be modified by the intended maintainers.” I’d say it’s simpler—it’s whether your code helps you or fights you when you need to fix, extend, or debug it.

The hidden costs of poor maintainability

Most of our time isn’t spent writing new code or tests—it’s spent understanding the old. That’s why maintainability isn’t just a nice-to-have. It’s the difference between shipping fast and getting stuck.

Poor maintainability creates cascading problems that compound over time. Here’s what happens when maintainability suffers in development and testing:

• Technical debt builds up quickly. Quick workarounds become permanent headaches that slow down both feature development and test automation.
• Bug fixes stretch from minutes to hours. You spend hours digging through confusing code just to figure out what went wrong.
• Test maintenance becomes a nightmare. Automated tests break constantly because they’re tightly coupled to unmaintainable code.
• Deadlines become impossible to meet. What should take weeks stretches into months of debugging, fixing flaky tests, and working around legacy constraints.
• Tests become unreliable. Poorly structured code makes it nearly impossible to write stable, meaningful tests.

Benefits of maintainability

Here’s what happens when you get maintainability right. These aren’t theoretical benefits; they’re real improvements that start showing up in your first sprint.

Research backs this up: Microsoft’s analysis of Windows 7 showed that the top 5% of well-maintained modules experienced significantly higher reductions in complexity and dependencies compared to poorly maintained code.

• Faster onboarding across teams. New developers and testers contribute meaningfully in their first few weeks, not their first quarter.
• Rapid bug resolution and test fixes. Issues get resolved quickly because both application code and test code tell you exactly what’s happening.
• Seamless test automation. Well-structured code makes it easy to write focused, reliable automated tests that catch bugs.
• Efficient testing workflows. Maintainable code enables better test isolation, faster test execution, and more predictable test results.
• Faster response to business changes. When stakeholders ask for new features or integrations, maintainable code means days instead of weeks. You’re building on a solid foundation rather than working around technical debt.
• Stress-free maintenance. Critical fixes and test updates happen quickly because readable code doesn’t hide surprises from either developers or testers.

Factors that affect maintainability

Understanding maintainability factors helps you avoid disasters like the one I experienced with the codebase, with variables like temp and x1 scattered everywhere. Here’s what makes code maintainable, so you never face the same disaster.

Code quality

Clean code saves time and sanity. When you write calculateCustomerDiscount() instead of calcStuff(), you’re communicating clearly with future developers, and they will easily comprehend what the method does.

Robert C. Martin put it perfectly: “You should name a variable using the same care with which you name a first-born child.” Those meaningless temp variables I inherited forced me into detective work instead of productive coding.

System architecture

Modular design prevents small changes from breaking the entire system. For example, when payment processing stays separate from inventory management, you can update one without breaking the entire system.

Code complexity

Complex code costs more to maintain. Every additional branch and nested condition increases the mental overhead required to understand your system.

When your developers know the codebase inside and out, they make updates faster and with fewer mistakes.

Team skills and experience

When your developers know the codebase inside and out, they make updates faster and with fewer mistakes.

But if they’re unfamiliar with how the system works, things slow down. Even small updates can take longer, and they may introduce new problems. They might repeat code that already exists or miss how one change affects another part of the app. That’s when things break.

Hidden bugs (latent defects)

Poor maintainability also creates hidden bugs that surface unexpectedly. In that same inherited codebase, confusing variable names like tempTotal and tempTotal_ led to a checkout bug where discounts and gift cards interfered with each other—a defect that went unnoticed for months because the logic was too complex to follow.

Clear variable names like cartTotal and discountedTotal would have prevented this entirely.

Development tools

Good tools make software maintenance faster and help reduce human error. Modern development environments are integrated with AI and can generate boilerplate code and catch issues before they become problems.

Challenges in maintainability

Writing code is only part of the job. Keeping it easy to update and understand over time is where the real work begins. As systems grow, these five issues often slow teams down:

Balancing speed and quality

Tight deadlines push teams to move fast, but cutting corners leads to technical debt—short-term solutions that cause long-term headaches. Instead, keep changes small, refactor regularly, and focus on writing modular code that is easier to build on.

Skipping testing

When teams skip testing to save time, bugs slip into production. These are harder to find later and much more expensive to fix in production. Use automated tests and clear standards to ensure testing becomes part of the workflow, not an afterthought.

Legacy code

Old code—especially without tests, structure, or docs—is harder to change without breaking things. Improve it safely by refactoring in small steps and writing tests as you go.

Changing requirements

Software evolves, so if the code isn’t flexible, even simple changes cause major disruptions. Modular design, version control, and regular team check-ins help teams adapt quickly.

Poor naming and code structure

Vague names like temp or calcStuff() slow everyone down. Clear, descriptive names and single-purpose functions make code easier to read, test, and reuse.

Maintainable code is clear, tested, and built with change in mind.

Best practices for maintainability

Maintaining software effectively requires using practices that make code easy to read, update, and test. These practical steps help teams build systems that stay reliable and flexible over time.

Clean code is easy to understand because it’s written with care.

Write clean, readable code

Clean code is easy to understand because it’s written with care. As Robert C. Martin says, “Clean code always looks like it was written by someone who cares.”

Here’s how to make your code easy to read.

• Use clear, meaningful names. Instead of calling a function calcStuff(), name it calculateCustomerDiscount(). This tells the reader exactly what the function does. Think of naming variables like naming a child—you want it to mean something special and clear.
• Keep functions short and focused. A function should do one thing. For example, don’t combine calculations, file reading, and logging all in one function. Break them up into smaller parts like readInvoiceFile(), calculateDiscount(), and logResults().
• Write helpful comments. Comments should explain why the code exists, not just what it’s doing. If you find yourself writing a comment like //add discount, it’s better to create a function called applyCustomerDiscount()—that way, the code explains itself.

Follow consistent coding standards

When everyone writes code the same way, it’s faster to read, easier to review, and simpler to fix. I once joined a project where half the team used snake_case and the other half used camelCase, which caused a lot of headaches.

camelCase or snake_case. Tabs or spaces. It doesn’t matter much—what matters is sticking to it as a team. Set up linters and formatters. They’ll catch small issues around spacing, indentation, and naming, so you don’t have to.

Design the code to be modular

Modular code is like building with LEGO blocks—each piece has a clear role and can be reused easily.

Start by keeping parts loosely connected. For example, don’t have your UserService (module that handles user-related actions) directly create emails. Instead, pass in an EmailSender so it can be swapped out later without changing the whole system.

Also, follow the don’t repeat yourself (DRY) principle. If you find yourself copying the same code in multiple places, turn it into a shared function or module.

Do regular code reviews

Regular code reviews will help catch issues early, thereby allowing the team to refactor and clean up messy code, which improves the overall quality of the codebase.

Also, encourage learning during reviews. When one developer reviews another’s code, they both learn. For example, if Mike reviews Sarah’s payment service code, he learns about the process. If Sarah reviews Mike’s test setup, she might pick up new ways to test her code.

Document decisions

Document your decisions as you go—what changed, why it changed, and how to run it. Keep your README clear, current, and easy to follow.

Clear docs save hours. When someone new joins the team, this will help them understand not just how the code works, but why it was built that way.

Use automated testing

Testing gives you confidence that your code works now and will keep working when changes are made later.

Start with unit tests, and test individual pieces of logic like calculateTax() or formatInvoiceDate() to make sure they always return the expected result.

After, do integration testing to test how different parts work together, like submitting an order and receiving a confirmation.

Test edge cases. For example, test what happens when a customer has a 100% discount or enters an empty shipping address.

Set up continuous integration (CI) to run all tests automatically every time someone pushes new code. This way, you’ll know immediately if something breaks.

Track and improve with meaningful metrics

Track things like code complexity, test coverage, and how long it takes new developers to make their first code change. Use this data to decide where to improve next.

Measuring and improving maintainability

Measuring maintainability helps you catch issues early—before they become more difficult and expensive to fix.

Start with measuring the maintainability index (MI). It combines several key stats: code complexity, length, and structure. For example, Microsoft recommends an MI above 20 to keep the code easier to update. If the score drops, it indicates that the code might need cleanup.

Now, here’s what else to watch:

• Cyclomatic complexity. Measures how many paths your code can take. More paths = more things to break.
• Lines of code. Shorter files, cleaner logic.
• Code coverage. Tracks how much of your code is tested. The more coverage, the safer your changes.

Want to keep your codebase maintainable? Here’s what works:

• Run static analysis tools regularly and integrate them into CI/CD pipelines.
• Set clear thresholds for complexity and test coverage. Define acceptable limits—like a maximum of 10 for cyclomatic complexity or 80% for test coverage.
• Monitor metric trends to catch issues early. For example, if a specific file becomes increasingly complex after each sprint, it might be due for refactoring before it becomes a bottleneck.
• Prioritize refactoring high-risk, high-change areas. Focus on the parts of your codebase that are both frequently updated and difficult to understand.
• Improve gradually by refactoring small parts and testing incrementally.

Code doesn’t need to be perfect. Just clean enough to build on without breaking.

Clean code, proper testing, documentation, and regular reviews are proactive strategies that keep the system reliable over time.

Final thoughts on maintainability

Maintainability means writing code that’s easy to understand, change, and grow with your product. It reduces technical debt, speeds up debugging, and makes onboarding smoother.

Clean code, proper testing, documentation, and regular reviews are proactive strategies that keep the system reliable over time.

Ready to make your codebase easier to manage? Start with Tricentis Tosca. It takes the pain out of test maintenance with model-based test automation. No more brittle scripts. Just reusable, easy-to-update tests that adapt as fast as your product does.

Tricentis SeaLights boosts maintainability with AI-driven insights that help teams test smarter, track coverage across all levels, and block untested code from release. It shortens test cycles, highlights risk areas, and ensures quality at every stage—so your codebase stays reliable, scalable, and ready for change.

Together, these tools reduce complexity, speed up updates, and support long-term maintainability.

Want to see how automation helps your code grow without breaking? Explore our software test automation guide, or try a Tricentis tool for yourself.

This post was written by Inimfon Willie. Inimfon is a computer scientist with skills in Javascript, Node.js, Dart, flutter, and Go Language. He is very interested in writing technical documents, especially those centered on general computer science concepts, flutter, and backend technologies, where he can use his strong communication skills and ability to explain complex technical ideas in an understandable and concise manner.