What Is Code Refactoring?
Refactoring reshapes code to make future work easier
At its core, refactoring focuses on restructuring code to improve its clarity, design, and maintainability while preserving all functional outcomes, e.g., better naming, cleaner abstractions, fewer duplicates, and more transparent data flow. The aim is to create a codebase where adding features or fixing defects becomes faster and less risky.
Example: Take a working system, make small internal changes that improve structure, and repeatedly verify behavior through tests.
Refactoring emphasizes incremental change, repeatable steps, and strong feedback through tests, it is practical and performance-neutral by design.
Refactoring legacy code in modern workflows
Modern workflows matured alongside automated testing and capable IDEs. Development teams run tests, apply a small change, rerun tests, and iterate. Refactoring supports continuous delivery, domain-driven design, and ongoing architectural evolution by keeping code adaptable and easier to navigate.
Note the important shift in perspective: Refactoring aims at preserving the software for the user while improving the quality for the software engineers to enable and facilitate long term maintenance.
Motivation for Refactoring
Teams refactor to remove friction in everyday work
When code is hard to read, difficult to test, or slow to change, refactoring streamlines workflows and prevents complexity from compounding. Primary motivations include:
- lowering cognitive load
- eliminating accidental complexity
- enabling safer changes
- improving performance focus
- aligning code with evolving business and architectural goals.
Code Smells are Indicators for the Need of Refactoring
What common code smells include
- long methods or classes that try to do too much
- duplicated logic
- excessive conditionals that blur intent
- “feature envy” where a class heavily manipulates another class’s data
- large parameter lists
- data clumps that travel together
- other signals include poor naming, unclear error handling, tight coupling, reliance on global state, and opaque side effects
How to decide where to refactor?
Identifying code smells helps you to decide also where to refactor because they indicate brittle areas. To detect code smells, the use of static analyzers is highly recommended.
Expert Tip: Join Prof. Rainer Koschke, Professor for Software Engineering and Co-Founder of Axivion for his webinar on-demand on “Bad Smell #1: The Science on Duplicated Code”
How Development Teams Benefit from Code Refactoring
Improved readability
Immediate results can be expected from improved readability.
- Clear names,
- smaller functions,
- coherent modules,
- and consistent patterns make intent visible at a glance.
Improved productivity
Readable code accelerates onboarding, code review, and cross-team collaboration. In this sense, the code refactoring meaning aligns closely with developer experience and day-to-day productivity.
-
Better collaboration emerges as the codebase becomes navigable and predictable.
-
Agreed principles and patterns promote shared components and reduce reinvention.
-
Clear boundaries lower merge conflicts, and well-factored units make pair programming, code review, and knowledge sharing more effective.
Tech debt reduction through refactored code
Software refactoring reduces technical debt by addressing shortcuts taken under schedule pressure. By deliberately improving design, teams avoid debt “interest” paid in slow delivery, fragile systems, and higher defect rates. Lower tech debt makes current and future work simpler and reduces operational risk.
The refactoring definition -in a practical way- is to reduce technical debt through small, verified changes that keep behavior intact.
Benefits in multi-language projects and cross-platform projects
In multilingual or cross-platform projects, consistent refactoring improves interoperability between front-end, back-end, embedded, and high-performance computing projects.
By aligning naming conventions, interfaces, and architectural boundaries across different stacks, teams reduce integration conflicts and facilitate traceability of behaviour throughout the overall system. This shared structural discipline helps maintain consistency even as components evolve independently in different languages, frameworks, or runtime environments.
Refactoring – a cornerstone in mission-critical contexts
Refactoring also enables performance and reliability work. Cleaner separation of concerns makes hotspots easier to locate and optimize, while explicit interfaces and reduced coupling improve testability and error isolation: This is valuable in safety-critical and regulated contexts where predictable behavior, traceability, and measured change are essential.
When you understand the refactoring definition as a structural improvement loop, it becomes a cornerstone of reliability.
Timing and Responsibility for Refactoring
When is the most effective time to refactor code?
The most effective time to refactor is when you are already working in the relevant area:
-
Refactor before adding a feature if the code is hard to extend
-
Refactor during implementation to keep changes clean, or immediately after to tidy up
-
Include refactoring in pre-release hardening to reduce risk and improve reliability
As a cadence, small, frequent refactorings are more effective than infrequent large efforts. Consistent code factoring prevents drift and keeps design decisions aligned.
Expert Tip: Integration of Axivion into IDEs: Analyse your changes locally, then commit and push (local build, single file analysis)
Who is responsible for the refactoring of legacy code?
Responsibility for refactoring is shared across roles:
-
Developers refactor as part of daily tasks
-
Technical leaders guide architectural-level refactoring
-
QA engineers provide robust tests to safeguard behavior
-
Product managers can sponsor time to reduce debt when it blocks delivery
-
Platform or core teams often lead cross-cutting initiatives to unify patterns and reduce duplication across services
Feature work and refactoring should coexist, with teams committed to maintaining code quality. Automation helps: static analysis, code formatters, and test coverage thresholds create guardrails that encourage good habits and drop risks.
Architectural Foundations and Refactoring
How refactoring helps to expose architectural gaps
Strong architectural foundations and refactoring reinforce each other: A well-structured architecture makes refactoring safer and more predictable, while routine refactoring ensures architecture health as the system evolves.
- Modularity: Clear module boundaries and minimal coupling reduce the blast radius of changes. Stable interfaces let you refactor internals without breaking consumers.
- Layering: Separation into presentation, application, domain, and infrastructure layers clarifies responsibilities and data flow. Layered designs make it easier to refactor logic without entangling concerns.
- Ports and Adapters: Hexagonal design isolates domain logic behind ports and adapts external systems via adapters. This pattern permits refactoring in the domain while keeping integrations steady.
- Dependency Management: Explicit dependency graphs, inversion of control, and dependency injection enable easier substitution and testing, reducing the cost and risk of refactoring.
- Domain-Driven Design: Rich domain models and bounded contexts establish business-aligned boundaries. Refactoring within a context remains contained, and ubiquitous language guides naming and intent.
To prevent architectural drift and erosion in scaling systems, regular code factoring is inevitable. It realigns implementation with architectural principles, prevents layer leakage, and maintains cohesion. Refactoring also exposes architectural gaps, like tight coupling, leaky abstractions, or misaligned boundaries.
To ensure the practice of refactoring, the constant and automatic use of an architecture verification tool is highly recommended. This prevents potential errors during refactoring and forms the plan and safety net for refactoring.
If you´re interested to evaluate Axivion Architecture Verification in your own development environment, choose a proof of value workshop and find out whether Qt Group´s sophisticated AV tool suits your needs.
Challenges of Code Refactoring
The bad reputation: Refactoring is "invisible"
Software refactoring often is described as invisible changes to existing code. In this context, invisible should not be confused with unnecessary.
Being invisible is the superpower:
Invisible is a great characteristic to describe the almost clandestine and constant improvement of source code that leads to faster responses, higher quality code and more confident security enhancements and performance applications.
After all, if the end user notices, the development team has done something seriously wrong, and the consequences range from costly recalls to life-threatening product complications, depending on their industry. We all remember the CrowdStrike-related IT outages in 2024.
3 types of risks
Software developers typically face 3 types of risk in their daily routines:
- Time - there is no time for the "invisible" changes now
- Budget - we have not money to waste for “invisible” changes
- Bugs - we do not want to introduce bugs and regressions
Refactoring legacy code can be impeded by limited test coverage, unclear ownership of legacy modules, tight timelines, fear of destabilising production, and lack of shared design principles. Without tests, even small changes feel risky. Legacy code often contains implicit behavior that is hard to preserve without characterization tests. Teams may hesitate when benefits feel deferred or intangible, especially if the code refactoring meaning is not shared across stakeholders. That´s why it is up to the leadership team to set the stage for refactoring.
The need of leadership
Leaders play a key role in creating the discipline needed for sustainable refactoring. They should set the expectation that improving code quality is not optional work but a strategic investment.
It is highly recommended to introduce metrics to create transparency around the value of refactoring:
- reduced cycle time
- fewer production incidents
- faster onboarding
- lower mean time to recovery
Tracking and communicating these metrics over time helps demonstrate incremental improvements and builds trust that refactoring efforts are delivering tangible results.
Principles like the “scout rule” by Robert C. Martin (aka Uncle Bob) - leaving code better than it was found - should be encouraged and supported.
When leadership defines refactor outcomes with metrics, trust grows.
Expert Tip: Why Technical Debt is a Leadership Problem
Watch our video broadcast with Annika Packalén and Miao Luo and learn from the teams that build the most reliable software.
Refactoring: The Bottom Line
Refactoring legacy code leads to improved maintainability and understandability of source code which will further motivate teams to deliver quality and keep code and architectural foundation clean. Never underestimate leadership that helps teams grow their potential by motivating them through demonstration and celebration of success as well as by providing the best possible workspace that offers the leading, most effective and holistic tools available on the market.
