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Zero-Downtime Database Migration Strategies for Production

Database migrations in production are terrifying — one mistake can corrupt data, cause downtime, or lock a critical table for hours. Yet every application needs them. This guide covers battle-tested strategies for running database migrations with zero downtime, including the expand-contract pattern, handling large tables, and reversible migrations.

Migration Strategies Compared

Strategy Downtime Complexity Best For

Expand-Contract Zero High Schema changes on high-traffic tables

Online Schema Change (gh-ost, pt-online-schema-change) Zero Medium ALTER TABLE on large MySQL tables

Blue-Green Database Near-zero Very High Major version upgrades, risky operations

Deploy + Migrate (simultaneous) Brief (seconds) Low Small apps with maintenance windows

Shadow Table Migration Zero Medium Reshaping or…