database-migrations

Zero-downtime database migrations use expand-contract strategies and concurrent indexing to apply schema changes safely. This involves separating schema and data migrations, adding nullable columns first, backfilling data, and updating application code before dropping old structures.

The best way to add columns and backfill data without table locks is separating schema migrations from data migrations. You add a nullable column, backfill rows asynchronously, update application code to use the new column, and enforce reversible UP/DOWN migrations to ensure safe rollback.

Yes, these database migration patterns work across ORMs like Prisma, Drizzle, TypeORM, and Django. They enforce reversible UP/DOWN migrations, explicit irreversibility marks, and separation of schema and data migrations to minimize production risk across PostgreSQL and MySQL.

To rollback a failed schema migration, you use explicit DOWN migrations or irreversibility marks applied during deployment. By enforcing UP/DOWN separation and separating schema changes from data backfills, you ensure database migrations remain reversible and minimize production downtime.

You should mark a database migration as irreversible when a safe rollback is impossible, such as after dropping columns or tables. Explicit irreversibility marks prevent accidental data loss during schema migrations and ensure zero-downtime deployment strategies remain intact.

Separating schema migrations from data migrations prevents locking and deployment failures in production databases. Keeping schema-only changes and data backfills as non-overlapping operations ensures safe, reversible patterns and enables zero-downtime database deployments across PostgreSQL and MySQL.