Why use migrations instead of automatic schema sync?

Definition:

A migration is a versioned database change that can be reviewed and applied deliberately. Automatic schema synchronization tries to match the schema to entity definitions and may make changes without a safe production rollout plan. Migrations make data changes, compatibility and deployment order explicit.

Key points:

• Migrations record intentional schema changes that can be reviewed.

• Automatic sync may make unwanted changes to production data.

• Plan compatibility between old and new app versions during deployment.

• Use an expand-and-contract rollout when old and new app versions need to run together during a deployment.

Interview point:

• A down migration is not guaranteed to restore deleted data; plan backups and forward fixes where needed.