Backend Migrate

When to Activate

• User wants to change an existing database schema
• User says "migration", "migrate", "schema evolution", "alter table"
• User needs to add, rename, drop, or change a column/table/index
• User asks about "backfill", "zero downtime", or "rollback migration"
• User needs to evolve schema without breaking running applications

Boundary: For greenfield schema design, use backend-db-design. This skill owns schema evolution only.

Prerequisites

See _shared/context-loading.md for standard prerequisites (project root check, manifest detection, shared file presence, memory fallback rules, and staleness check).

Migration-specific prerequisites below: