Zero-Downtime Database Migrations: Changing the Engine Mid-Flight | Clickmasters

Certain operations lock tables in certain engines; know which, use online-migration techniques, and batch backfills with throttling — the 'quick ALTER' that froze production is a classic.

Compatibility across app versions during rollout (old code + new schema, new code + old schema) — the choreography that makes canary and blue-green possible at all.

Skipping the discipline this article describes until an incident, audit, or stalled project forces it — every practice above is cheaper adopted early than retrofitted under pressure.