How to Approach Code Refactoring: Strategy, Practice, Mindset

November 11, 2025

Refactoring is a process, not an event

“Any code that isn’t undergoing refactoring is rotting.” Martin Fowler’s line from Refactoring: Improving the Design of Existing Code still rings true. Refactoring is the ongoing maintenance discipline that keeps change affordable and risk contained. Empirical work by Bavota et al. (IEEE TSE 2015) shows that postponing refactoring increases defect rates, maintenance costs, and team churn. A more recent ICSE 2023 study (O’Reilly et al.) highlights that teams who refactor iteratively ship features faster and keep defect density lower.

Start with diagnosis

Before touching a single line, answer three questions:

Where does it hurt the most?
• long-standing tech debt,
• areas of tangled “spaghetti” code,
• clusters of incidents in the postmortem logs.

What signals does the system send?
• core numbers: how complex the code is, how long the build takes, how fast we recover,
• repeating review comments,
• a growing number of workarounds and flags.

What business value will we unlock?
• faster delivery of new capability,
• reduced support effort,
• better compliance and reliability posture.

Planning: intent, scope, priorities

Kent Beck insists on “intentional refactoring”: every step needs a goal. A simple plan structure helps:

Business objective – e.g. “Shorten reporting time by 30%”, “Reduce incidents in the billing module”.
Technical scope – modules to reshape, dependencies to retire.
Expected outcome – target metrics (coverage, complexity), control dates, accountable owners.
Exit criteria – when diminishing returns kick in, move on to the next hotspot.

Make it safe: tests and characterization

Michael Feathers reminds us that refactoring without tests is gambling. Prior to any change:

add unit and integration tests where possible,
lean on characterization tests to capture current behaviour,
tighten observability (logs, traces) so staging/prod feedback is immediate,
keep the CI/CD pipeline fast – feedback cycles should be measured in minutes.

If testing is difficult (poor isolation, legacy systems), refactor by extraction (Extract Class/Module) and wrap legacy sections behind facades to regain control.

Step-by-step execution

1. Map the problem:

identify hotspots via tools (SonarQube, CodeScene) and internal data,
talk with support/DevOps about high-impact incidents and the cost of mitigation,
trace the user journey to see which parts of the system customers touch most.

2. Make small, reversible moves:

apply micro-refactorings (Small Steps, Composed Method, Parameterize Method),
keep the build green after each move,
commit frequently, avoid “giant refactor” branches,
follow Robert C. Martin’s Boy Scout Rule: leave the code better than you found it.

3. Integrate and review:

keep pull requests focused, with context and acceptance notes,
use review checklists (does the scope match the plan? did the metrics move?),
demo the change to stakeholders beyond engineering – highlight which constraints are gone.

Measuring impact

Combine technical, operational, and business indicators:

Technical: complexity, coupling, static warnings, coverage, dependencies.
Operational: MTTR, deploy time, number of rollbacks, environment failures.
Business: feature lead time, customer support hours, cost of ownership.

Make it cultural

Sustainable refactoring depends on habits:

budget 10–20% of sprint capacity for tech debt reduction,
put tech debt on the roadmap like any other product capability,
expose the cost of not refactoring (support hours, outage impact),
share patterns and anti-patterns through guilds, workshops, pair programming,
maintain Architecture Decision Records so design choices remain transparent.

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Need a second pair of eyes?

If you’d like an independent assessment of where to start, or need help steering a legacy transformation, I offer:

system audits and tech debt reviews,
guidance on planning refactoring and delivering safe changes.

Let’s talk when you’re ready to bring your legacy up to modern standards.