How do you design a data migration strategy?

Question

Accepted Answer

**Data migration** — moving data between systems or formats.

**Phases:**
1. **Assessment:** Inventory data, quality, dependencies.
2. **Planning:** Strategy, timeline, rollback plan.
3. **Design:** Mapping, transformation rules.
4. **Development:** ETL scripts, validation.
5. **Testing:** Data validation, reconciliation.
6. **Execution:** Cutover, parallel running.
7. **Validation:** Post-migration checks.

**Strategies:**
- **Big bang:** Migrate all at once (short downtime).
- **Trickle:** Gradual migration (zero downtime).
- **Hybrid:** Migrate in phases by domain.

**Validation:**
- Record counts (source vs target).
- Checksums for data integrity.
- Business rule validation.
- Performance benchmarks.

**Challenges:**
- Data format differences.
- Referential integrity across systems.
- Downtime management.
- Rollback procedures.

**Tools:**
- AWS DMS, Azure Data Migration.
- Apache NiFi, Talend.

Systems Analyst: How do you design a data migration strategy?