Plan zero-downtime database migrations

Design safe, reversible schema changes for production databases

When you must alter production schema without downtime and need to prove rollback works.

• · migration scripts (DDL/DML)
• · test data (production-size)
• · rollback plan

• · applied migration
• · documented rollback procedure
• · tested against production copy

• · PostgreSQL / MySQL
• · Prisma / Drizzle / Kysely / Django / TypeORM / golang-migrate

• · migration reversible or explicitly marked irreversible
• · no full table locks on large tables
• · new columns nullable or have defaults

• · applied migration without down() defined
• · NOT NULL without default on large table (full rewrite)
• · concurrent index created inside transaction

• · migrate tested against production-sized data
• · expand-contract pattern used for column renames
• · batched updates with SKIP LOCKED