Twenty four years, ten DB migrations, zero downtime

Short summary

After a seven-minute downtime in 2006, this ops engineer developed a zero-downtime database migration pattern used for 24 years across 10 migrations. The approach separates user-facing data from aggregates, using incremental copying and dual-write/read modes to eliminate service interruptions. Each step tolerates mixed states across instances, enabling gradual rollout without coordinated restarts.

• •Seven-minute downtime incident in 2006 motivated a pattern that achieved zero downtime across 24 years and 10 migrations
• •Pattern separates Data A (user-facing) and Data B (aggregates) with different synchronization strategies
• •Uses incremental copying, dual-write mode, and gradual read switchover to eliminate downtime while tolerating mixed deployment states

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