Database Migration Patterns

Safe, reversible database schema changes for production systems.

When to Activate

• 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

Core Principles

1. Every change is a migration — never alter production databases manually
2. Migrations are forward-only in production — rollbacks use new forward migrations
3. Schema and data migrations are separate — never mix DDL and DML in one migration
4. Test migrations against production-sized data — a migration that works on 100 rows may lock on 10M
5. Migrations are immutable once deployed — never edit a migration that has run in production