safe-schema-migrations

name	safe-schema-migrations
description	Evolve schemas without downtime: expand/contract (add -> backfill in batches -> switch -> drop) across separate deploys, lock-aware DDL (create indexes CONCURRENTLY, nullable-add-then-validate), reversibility, and ordered versioned migrations.

Safe Schema Migrations

Expand/contract

Add new (safely) -> backfill in batches -> dual-write/switch reads -> drop old. Across separate deploys. A rename = add-copy-switch-drop, not ALTER RENAME mid-traffic.

Lock awareness

Volatile-default add, type change, or SET NOT NULL can lock the table. Use: nullable add + batched backfill + ADD CONSTRAINT ... NOT VALID then VALIDATE; create indexes CONCURRENTLY.

Reversible + ordered

Every migration has a down path / tested rollback. Versioned, ordered, never edit a shipped migration. Sequence with devops-cicd/release-engineer.