database-migrations

Zero-downtime database migrations use expand-contract workflows, concurrent index creation, and separate DDL and DML execution to apply schema changes without disrupting production traffic. This approach enforces safe column additions and reversible schema evolutions.

An expand-contract workflow is a phased migration pattern that separates schema expansion, data backfill, and schema contraction to preserve data integrity. It allows safe column additions and renames while keeping the application functional throughout the migration.

Safe concurrent index creation in PostgreSQL requires explicit rules for concurrent index deployment to avoid locking tables. This Skill enforces these rules as part of a zero-downtime migration plan to maintain database availability during schema evolutions.

The best way to plan a rollback is to document robust rollback strategies and separate DDL and DML migrations in advance. This ensures migrations are reversible and allows safe recovery if schema changes fail in production.

Testing migrations against production-sized data is necessary to validate performance and prevent timeouts during schema evolutions. It verifies that concurrent index creation and data backfills execute safely under realistic load before reaching production.

You need to separate DDL and DML migrations when performing data backfills and zero-downtime schema changes in production. This separation prevents locking conflicts and ensures data integrity throughout the expand-contract workflow.