Backend Migrations

Reversible migrations use paired up() and down() methods to safely evolve your schema. Design migrations to remain compatible with existing code during deployment—add nullable columns before populating them, and avoid breaking changes that require simultaneous code and schema updates.

Add the column as nullable first, deploy the code that uses it, then backfill existing rows and remove the nullable constraint in a follow-up migration. This approach keeps your application running throughout the schema change.

Database migrations include rollback logic in the down() method. Execute the rollback command to reverse the last migration, restoring your schema to its previous state. Always test rollbacks in staging before deploying to production.

Yes. Create indexes in separate migrations and use strategies like online index creation (framework-dependent) to avoid locking tables. Plan index changes during low-traffic windows or use background migration techniques for minimal disruption.

Separating them reduces migration complexity and risk. Schema migrations handle table structure; data migrations handle population and transformation. This lets you deploy schema changes independently and rerun data migrations if issues arise.

Yes. Version control tracks migration history, enables rollbacks, and ensures team alignment on schema evolution. Migration files must be immutable once deployed—create new migrations instead of editing existing ones.