Refactor Smart Today, Move Faster Tomorrow — Part 2: Plan Your Refactor Step by Step

[Agustín Rodríguez]

So, you've confirmed that your refactor is necessary.
Now it's time to plan it right — because a poorly scoped or unstructured refactor is a trap that can drain weeks of work and leave everything worse than before.

Let's break it down.

Choose the Right Strategy​

There's no single "best" approach to refactoring, but here are common strategies — and when to use them:

1. Incremental Refactor (Recommended for Live Systems)​

Refactor bit by bit, keeping the system functional at all times.

Pros: Safe, gradual, easier to test
Cons: Requires discipline and clear boundaries
Best for: Actively used systems, critical codebases, or anything in production

2. Branch-based Refactor (When Changes Are Too Invasive)​

Fork the code into a separate branch, refactor freely, and merge later.

Pros: Total freedom to redesign
Cons: Merge hell, risk of long-living branches, hard to keep in sync
Best for: Isolated modules, internal tools, greenfield components

3. Strangler Fig Pattern (Great for Legacy Systems)​

Wrap and slowly replace legacy logic, one endpoint or feature at a time.

Pros: Legacy coexists with new code, safer evolution
Cons: Requires architectural support (e.g., routing layers, boundaries)

Control the Scope or You'll Never Finish​

One of the biggest risks in a refactor is the infinite scope creep.
You touch one piece, which leads to another, and then another... and before you know it, it's a rewrite.

Avoid this by:

• Defining clear boundaries — "Only refactor the email dispatch logic"
• Having non-negotiable out-of-scope rules — "Don't rewrite the frontend now"
• Splitting the work into atomic, testable steps

Tip: Track tasks in a checklist. Treat each step like a mini-feature.

Pick an Architecture or Pattern (Don't Wing It)​

Before you start moving code around, ask yourself:
What kind of structure are we aiming for?
Without a vision, you'll likely make it different, not better.

Examples:

• Clean or Hexagonal architecture
• Adapter pattern to swap external services
• Strategy pattern to simplify logic by behavior
• Service layer for reusable business logic
• Ports and adapters to isolate frameworks

Refactor is not just renaming variables — it's about redesigning how things work internally.

Stabilize Interfaces (Create Contracts)​

Even during a refactor, some parts of your system can't change — external APIs, third-party expectations, or other modules still depending on them.

• Define stable interfaces or DTOs (data transfer objects)
• Keep method signatures consistent while you migrate under the hood
• Use adapters to convert legacy format to the new one temporarily

This makes it easier to refactor one part without breaking everything else.

Use Feature Flags​

If your refactor affects a feature that's already live, wrap the new version in a flag so you can:

• Test it in staging
• Gradually roll it out
• Roll back instantly if needed

This adds safety — especially when combined with CI/CD pipelines.

Define a Refactor Testing Strategy​

You need different levels of tests to support your refactor:

• Unit tests for small modules
• Integration tests for connections between modules
• Regression tests to make sure nothing breaks
• (Optional) Snapshots or visual diffs for UIs

Also, use coverage tools to find untested danger zones before you touch them.

Checklist Before the First Commit​

Before writing any code:

• [ ] Refactor strategy selected (Incremental, Branch, Strangler)
• [ ] Scope clearly defined and limited
• [ ] Architectural target or pattern chosen
• [ ] Interfaces/contracts stabilized
• [ ] Feature flags planned (if needed)
• [ ] Tests prepared or planned
• [ ] Metrics defined (to validate results later)

Cover image credit: Chris Ried, via Unsplash

Continue reading...

 

Join 𝕋𝕄𝕋 on Telegram
Channel PREVIEW: