Advanced AI Prompt for Zero-Downtime Database Migrations in CI/CD

Act as a Database Reliability Engineer (DBRE). Develop an airtight GitHub Actions strategy for executing zero-downtime database schema changes utilizing the 'Expand and Contract' (Parallel Change) architectural pattern for a [DATABASE_TYPE] system. The workflow must utilize [MIGRATION_TOOL] (e.g., Flyway or Liquibase) and be decoupled into highly specific jobs: Job 1) 'Expand' - Apply purely additive, non-locking SQL schema changes. Job 2) 'Deploy' - Roll out the new [APPLICATION_FRAMEWORK] code that writes to both old and new columns. Job 3) 'Migrate' - Execute a background script to backfill data into the new columns. Job 4) 'Contract' - A manually triggered gate that drops the deprecated columns only after verifying 100% data consistency. Explicitly define how [BACKUP_STRATEGY] is executed programmatically before Job 1 begins.