Zero-Downtime Database Migration Pipeline

System Design diagram · made in Skemio

Architecture diagram illustrating zero-downtime database migration: API Gateway sends writes to an App Server, which dual writes to legacy and new tables while a backfill worker migrates historic rows.

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What it shows

Expand-and-contract pattern keeps backward compatibility during changes
Dual writes safeguard against data drift before cutting over reading logic
Background workers backfill cold rows asynchronously without table locks

The takeaway

Never rename or drop columns in-place; write new, backfill old, read new, then contract.

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