Schema Migration overview

Safe, audited workflow for evolving database schemas in production without downtime or data loss. The data engineer authors a migration script and a corresponding rollback script, both reviewed by a backend engineer for correctness and performance impact on large tables. Migrations are tested against a production-sized data snapshot in a staging environment with execution-time profiling. The migration is applied to production in a maintenance window or via a zero-downtime strategy (expand-contract pattern), and automated integrity checks verify row counts and index health after completion.