database-migrations

Zero-downtime database migrations use an expand-then-contract strategy to modify schemas without locking tables. You expand the schema with backward-compatible changes, backfill data in batches, and contract the old schema after application cutover.

The safest way to add a non-nullable column during a database migration is to create it with a default value or as nullable. You then backfill existing rows in batches before enforcing constraints and dropping deprecated fields.

Yes, this approach works with ORM-driven workflows including Prisma, Drizzle, Django, TypeORM, and golang-migrate. It provides guided migration patterns to ensure safe schema changes across PostgreSQL and MySQL production environments.

Planning a rollback for a failed production database migration involves defining explicit reversal steps for each schema change. You must account for data backfills and ensure backward compatibility so the application can safely revert to the previous database state.

Automated database migrations for large datasets require careful batch sizing during data backfills to avoid locking issues. You must also maintain backward compatibility throughout the multi-phase expand and contract process to prevent application downtime.