Reducing technical debt: causes, measurement, approach
Technical debt slows your team every day: every new feature takes longer, every change creates unintended side effects, and onboarding new developers takes weeks.
What is technical debt?
Technical debt is the future extra cost that arises when software is built faster or simpler than would be sensible in the long run. The term comes from Ward Cunningham: as with a loan, the team pays interest – in the form of slower changes, more bugs and higher maintenance effort – until the debt is repaid through refactoring.
Types of technical debt
Code debt
Duplicated code, overly long functions, unclear names and missing structure. It slows every change and is the most visible form – but rarely the most expensive.
Architecture debt
Modules that connect everything with everything, missing interfaces, data models that no longer carry new requirements. It slows whole teams and can only be reduced in a planned way.
Test debt
Missing or brittle tests. Every change becomes a risk and releases are delayed because manual checks are needed.
Dependency & infrastructure debt
Outdated frameworks, libraries without security updates, manual deployments. It goes unnoticed for a long time – until an upgrade or a security incident forces the issue.
Measuring technical debt
Debt cannot be priced exactly in euros, but a few metrics make it visible and comparable.
Change frequency × defect density
Files that change often and cause bugs often are the most expensive hotspots. This combination of version history and bug tracker shows where reduction pays off first.
Lead time for changes
How long does a small change take from idea to release? If this time grows over months, the debt is growing – regardless of what the code looks like.
Test coverage & static analysis
Coverage of critical paths, number and severity of findings from tools such as SonarQube or ESLint. Useful as a trend, not as an absolute number.
Age of dependencies
How many major versions are the framework and libraries behind, how many known vulnerabilities are open? This number determines the upgrade risk.
Technical Debt, Tackled Systematically
We analyse existing code systematically, prioritise debt by actual impact, and reduce it so your team becomes measurably faster.
The essentials of Technical Debt Reduction
- We analyse existing code systematically, prioritise technical debt by its actual impact, and reduce it so your team becomes measurably faster.
- We prioritise by change frequency and defect density, because debt in the daily-touched core slows every feature, while in stable code it does little harm.
- Before reworking code, we secure existing behaviour with characterisation tests as a safety net for structural improvements.
- We integrate targeted refactoring into the normal development rhythm, so every new feature leaves the code better than it found it.
- With code reviews, static analysis in the CI pipeline, and architecture fitness functions, we prevent new debt from quietly becoming the norm.
- New features take longer and longer even though the team hasn't shrunk — technical debt slows progress daily.
- Changes to one module regularly create unintended side effects in other parts of the system.
- New developers need months to become productive because the codebase is poorly documented and hard to understand.
Analysis and Prioritisation
Not all technical debt is equally harmful. We analyse code quality, test coverage, dependency structures, and architectural smells systematically, prioritising debt by its actual impact on development speed and system stability — so resources are invested where leverage is greatest.
Incremental Reduction
Technical debt can rarely be eliminated in a single sprint. We integrate targeted refactoring into the normal development rhythm: every new feature leaves the code better than it found it. Clear quality metrics and definition-of-done criteria prevent new debt from accumulating.
Building Test Coverage
Refactoring without tests is risky — you never know whether a change broke something. We build test coverage deliberately where refactoring is planned: characterisation tests document existing behaviour before we change it, serving as a safety net for structural improvements.
Sustaining Quality
Technical debt re-accumulates when quality standards aren't enforced. We establish code review processes, static analysis in the CI pipeline, and architecture fitness functions that verify structural rules automatically — so debt doesn't become the default again.
Where debt actually slows you down
Not all technical debt is equally harmful. What matters is the combination of change frequency and bug density — together they reveal where reduction delivers real speed gains.
high bug densitylow bug density
Old utility code with bugsPublic API with errors
Core with debt – highest priorityNew features with workarounds
Stable legacy code
Active code, clean
rarely changedtouched daily
Only the top-right quadrant justifies immediate action.
From debt audit to lasting quality
Debt reduction is not a one-off project but a controlled four-phase process — from assessment through to embedding quality into everyday workflows.
Analysis & prioritisation
Measure the codebase: change frequency, bug density, coupling. Prioritise debt by actual drag on velocity, not by instinct.
Build characterisation tests
Lock down existing behaviour with tests before changing a single line. The safety net that makes bold refactoring responsible.
Incremental debt reduction
Refactor high-priority modules in parallel with live operations. Small, traceable steps instead of a big-bang rewrite.
Sustain quality long-term
Embed code reviews, static analysis, and a clear definition of done into daily work so new debt never silently becomes the norm.
Each phase builds on the safety net established by the previous one.
What matters for Technical Debt Reduction
Reducing debt does not mean tidying everything but tidying the right thing. Not every debt is equally harmful: messy code in a stable, rarely changed module costs almost nothing, while the same debt in the daily-touched core slows down every new feature. Prioritising by change frequency and defect density is therefore the decisive first step.
Refactoring without tests is dangerous, because you do not know whether you are preserving behaviour or breaking it. Characterisation tests capture existing behaviour before it is changed and create the safety net that makes bold interventions justifiable in the first place. Only this net turns risky tinkering into controlled improvement.
A one-off cleanup without changing the way of working is wasted effort, because new debt forms again immediately. What makes the difference are everyday quality processes: code reviews, static analysis, and a clear definition of done that prevents sloppy work from quietly becoming the norm. Reducing debt is a habit, not a project with an end date.
Related goal: Replace legacy systems
Not all debt is equal
Technical debt in rarely changed, stable code is less harmful than debt in the core of the system. Prioritising by change frequency and defect density shows where reduction actually returns development speed.
Tests are the safety net
Refactoring without test coverage is flying blind. Characterisation tests document existing behaviour before it is changed — creating the confidence needed for bold, structural refactoring.
Debt accumulates again
One-time debt reduction without quality processes is wasted effort. Code reviews, static analysis, and clear definition-of-done prevent new debt from creeping back in as the default.
Win back your speed
With us you're always at the forefront of enterprise software development and benefit directly from our extensive development know-how. Together we examine your business processes, identify key optimization potential and develop individually tailored solutions. Your business goals and expectations are the focal point of everything we do.
Comprehensive technological expertise
We choose the stack per project by requirement and rely on established, future-proof technologies instead of niche dependencies.
Specialized in enterprise solutions
The real lever lies in clean interfaces: we integrate deeply into ERP, CRM and third-party systems instead of isolated solutions.
Years of experience in the software industry
From requirements analysis to operation after go-live, we know the pitfalls of large software projects.
Multidisciplinary expert team
Analysis, architecture, backend and operations come together in one team, without friction between disciplines.
Long-term business success
We build maintainable foundations that grow with your company, and stay by your side with support and further development.
Is your old system a risk?
Six questions on framework, version, maintenance, hosting and documentation – in two minutes you get a risk score and the matching modernization path: refactor, strangler or rebuild.
Start the legacy checkFrequently asked questions
Your question isn't here? Ask us directly
How do I explain to management why debt reduction takes time?
By expressing it in business terms: technical debt slows new features, increases error rates, and extends onboarding time for new developers. We help you make the connection between code quality and development speed measurable and communicable.
Should we refactor everything or only critical areas?
Only critical areas — specifically those causing the most pain. Complete refactoring is rarely economical. We identify the parts of the codebase changed most frequently with the highest defect density — that's where debt reduction delivers the fastest return.
How do you prevent new technical debt from forming while we reduce old debt?
Through consistent quality standards: definition-of-done criteria, code reviews with an architectural perspective, and static analysis in the CI pipeline. New debt mostly arises from missing standards and absent review processes, not malicious intent.
Last updated on
READY FOR SOFTWARE BUILT AROUND YOUR BUSINESS?
Related articles from our blog