Every successful application eventually outgrows its original architecture. What started as a clean, well-structured monolith becomes a tangled web of dependencies where changing one feature risks breaking three others. Deployments become risky, test suites take forever, and developers spend more time navigating the codebase than writing new features. The instinct is to rewrite. Do not. Rewrites are how engineering teams burn months of effort and deliver something that, at best, does what the old system already did. The better approach is incremental migration: systematically extracting capabilities from the monolith while keeping the system running in production the entire time. I have led these migrations across multiple companies — taking legacy codebases with 15+ modules, hundreds of database tables, and years of accumulated technical debt and transforming them into modular, maintainable architectures without downtime. This article is the playbook.…