DB Migration Strategy

Overview

Use this skill to evolve schemas in production without service disruption or hidden data corruption.

Scope Boundaries

• Schema changes affect live read/write paths.
• Multiple service versions must coexist during rollout.
• Data backfill or contract transition is required.

Core Judgments

• Migration pattern: expand-contract, dual-write, shadow-read, or phased cutover.
• Compatibility window duration and supported versions.
• Backfill approach and execution safety.
• Rollback semantics and data reconciliation strategy.

Practitioner Heuristics

• Prefer additive/compatible changes before destructive cleanup.
• Separate schema deployment from application behavior switch.
• Dual-write without reconciliation plan is a corruption risk.
• Large backfills need throttling and progress observability tied to business impact.

Workflow

1. Define change classes: additive, transitional, destructive.
2. Sequence schema and application releases for compatibility.
3. Plan data migration/backfill and failure handling.
4. Define cutover trigger and rollback decision points.
5. Execute deprecation/removal only after compatibility window closes.
6. Document residual migration debt and retirement deadlines.

Common Failure Modes

• Breaking changes shipped before all consumers are updated.
• Backfill jobs compete with production traffic and cause incidents.
• Rollback plan restores code but not data semantics.

Failure Conditions

• Stop when compatibility window cannot be supported operationally.
• Stop when rollback semantics for migrated data are undefined.
• Escalate when migration risk exceeds release risk tolerance.