Refactoring at Scale

In Refactoring at Scale, software architect and engineering leader Maarten Smeets reveals how high-performing teams transform fragile, aging systems into scalable platforms-without breaking production or slowing down delivery.

Drawing on real-world lessons from large engineering organizations, this book presents a practical framework for safely evolving complex systems while your business continues to run.

You'll learn how to:

• Turn risky "big rewrites" into safe, incremental refactoring strategies

• Identify high-leverage improvements hidden inside legacy systems

• Use testing, observability, and architecture patterns to reduce change risk

• Align engineering teams around continuous modernization

• Scale refactoring efforts across large codebases and multiple teams

• Replace technical debt with technical leverage

Packed with battle-tested techniques, architectural patterns, and organizational strategies, Refactoring at Scale shows how the best engineering teams modernize their systems without stopping the world.

Whether you're a staff engineer, architect, or engineering leader responsible for long-lived systems, this book will help you turn legacy code from a constraint into a competitive advantage.