addy-deprecation-and-migration

Legacy API deprecation requires structured governance to plan, evaluate replacements, and execute a safe migration path for users. You define decision criteria, build migration tooling, and apply sunset strategies to ensure the new implementation is production-ready before shutting down the old system.

The Strangler pattern is a migration strategy that gradually replaces legacy components by routing functionality to new implementations. Use it when sunsetting an API or consolidating duplicate implementations, allowing safe transition without a risky big-bang rewrite.

Migrating users to a replacement service is best handled by combining feature flags, adapters, and migration guides. This structured approach provides governance and tooling to ensure the new service handles production traffic safely before the old system is sunset.

Migration guides for consolidating duplicate implementations must document the sunset strategy, replacement evaluation criteria, and step-by-step transition paths. They provide governance and tooling to ensure replacements are production-ready and old systems are safely sunset.

Deprecation and migration governance applies to planning, documenting, and executing sunset strategies across organizations. It supports sunsetting APIs, migrating users to new services, and consolidating duplicate implementations by providing structured tooling and replacement evaluation.

A gradual migration approach using adapters or feature flags may not suit legacy code when replacements cannot achieve production-ready status or when governance criteria for safely sunsetting the old system are not met. Ensure the new implementation handles all required functionality before proceeding.