What problem does it solve? Removing old systems, APIs, and features is risky because consumers depend on undocumented behaviors, and in-place database schema changes break running code during rollouts. This Skill provides a disciplined process for deprecating systems, migrating consumers safely, and evolving production schemas without downtime. ## Core Features & Use Cases - Deprecation Decision Framework: Evaluate whether to maintain or sunset a system by quantifying consumers, migration cost, and ongoing maintenance cost, with advisory vs compulsory deprecation guidance. - Migration Patterns: Apply the Strangler pattern, Adapter pattern, and feature-flag cutovers to move consumers incrementally from old implementations to replacements. - Expand/Contract Schema Migrations: Rename or drop database columns in production through additive phases (expand, dual-write, backfill, contract) so old and new code stay valid at every deploy. - Use Case: You need to rename a name column to full_name in a live Postgres database. The Skill walks you through adding the nullable column, dual-writing, backfilling in batches, switching reads, and dropping the old column in a separate deploy. ## Quick Start Ask the agent to plan a deprecation and migration path for your legacy service or to design an expand/contract migration for renaming a production database column.
