db-migration-strategy

Schema migration patterns like expand-contract, dual-write, shadow-read, and phased cutover minimize downtime during production rollouts. Expand-contract separates changes into backward-compatible stages, while dual-write and shadow-read validate data across coexisting service versions before cutover.

Coordinate database backfills during a multi-version rollout by defining compatibility windows where old and new service versions coexist. Use shadow-reads or dual-writes to populate and validate data before completing the phased cutover.

Yes, the expand-contract pattern avoids downtime during schema migrations by expanding the schema first, deploying code to use it, and contracting later. This keeps multiple service versions compatible throughout the rollout window.

Define rollback semantics for a failed production schema migration by documenting data reconciliation steps and criteria before deploying. Plan the compatibility window so you can revert to the prior service version without losing data integrity.

You need a shadow-read strategy for database migrations when validating a new schema or data path against production traffic without impacting users. It verifies data integrity during the compatibility window before executing a full phased cutover.

Dual-write migrations for production schema changes require careful handling of consistency and reconciliation if the rollout fails. You must maintain strict compatibility windows and manage the complexity of writing to both old and new schema versions simultaneously.