database-migrations

Safe, reversible database schema changes for production systems. Before applying any migration: Never rename directly in production. Use the expand-contract pattern: For operations Prisma cannot express (concurrent indexes, data backfills): Remove a column from the Django model without dropping it from the database immediately: For critical production changes, follow the expand-contract pattern: - Covers PostgreSQL, MySQL, and five major ORMs (Prisma, Drizzle, Django, TypeORM, golang-migrate) with workflow examples and schema patterns for each - Enforces core principles: immutable deployed migrations, forward-only production rollbacks, and separation of schema (DDL) from data (DML) migrations - Provides the expand-contract pattern for zero-downtime column renames and large refactors, with concrete timeline examples - Includes safety checklist, anti-patterns table, and detailed PostgreSQL recipes for concurrent indexes, batched updates, and NOT NULL column additions without table locks - Creating or altering database tables - Adding/removing columns or indexes - Running data migrations (backfill, transform) - Planning zero-downtime schema changes - Setting up migration tooling for a new project - Every change is a migration — never alter production databases manually - Migrations are forward-only in production — rollbacks use new forward migrations - Schema and data migrations...