What problem does it solve? Removing old systems, APIs, and features is hard because users depend on existing behavior, and rushed removals or in-place schema changes cause outages. This Skill provides a disciplined process for deciding what to deprecate, migrating consumers safely, and executing zero-downtime database schema changes. ## Core Features & Use Cases - Deprecation Decision Framework: Structured questions to decide whether to maintain, sunset, or replace a system, including advisory vs compulsory deprecation guidance. - Migration Patterns: Step-by-step guidance for the Strangler pattern, Adapter pattern, and feature-flag-based cutovers, plus the Churn Rule for owning user migration. - Expand/Contract Schema Migrations: A phased approach (expand, dual-write, backfill, switch reads, contract) for renaming or dropping database columns without downtime. - Use Case: You need to rename a name column to full_name in a production Postgres database. The Skill walks you through adding the new nullable column, dual-writing, backfilling in batches, switching reads, and dropping the old column in a separate deploy. ## Quick Start Ask the assistant to plan a safe migration for renaming a production database column using the expand and contract approach.
