A breaking change crosses a service contract boundary in a way that can affect dependent services. Standard contracts make that boundary visible while capabilities are separated from a legacy application. section 16.1
Use contract boundaries to manage modernization risk:
- Define well-known contracts between independently deployable business-domain services. section 16.1
- Test an extracted or rewritten capability in isolation before changing dependent services. section 16.1
- Prefer incremental extraction when business goals and investment appetite favor smaller modernization steps. section 16.1




