Migrating a PHP monolith to a decoupled architecture without breaking everything

Migrating an aging PHP monolith to a modular architecture requires a progressive strategy to avoid downtime.

Recipe

1. Diagnose with Deptrac.
2. Avoid 20-microservice big-bang. Find natural domain boundaries.
3. Modularize in-place first.
4. Strangler pattern on lower-risk domains.
5. Outbox for cross-boundary communication.
6. Extract progressively, keep low-risk pieces in the monolith.