Maintainability

Parallel Change for Safe Interface Refactoring

Changing a shared interface is risky when many callers depend on it. A large “update everything at once” patch can work in a small codebase, but it becomes harder to review, deploy, and roll back as dependencies spread across modules or services. Parallel change is a refactoring technique that keeps old and new interfaces working side by side for a limited period. The migration happens in three stages: expand, migrate, and contract.