Cloud & Infrastructure Practical By Samson Tanimawo, PhD Published May 2, 2026 4 min read

Database Migration in Cloud: The Three-Phase Rule

Cloud database migrations have specific risks. The three-phase pattern adapted for cloud-native databases.

Three phases

Phase 1: dual-write to old and new. Backfill historical.

Phase 2: dual-read; primary is the new. Old is fallback.

Phase 3: drop old.

Use AWS DMS, GCP DataStream, or equivalent for the dual-write.

Verify replication lag during phase 1; production traffic should not see staleness.

Phase 1 → drop new tables.

Phase 2 → flip primary back.

Phase 3 → no rollback. Plan accordingly.