Migrations fail in predictable ways: unmapped fields silently dropped, duplicates multiplied, consent records lost, and a go-live weekend nobody can roll back. All four are preventable with process.
Before you move anything
- Inventory every object and field in the old system, and decide: map, archive, or drop — explicitly.
- Choose dedupe keys and test them on real exports.
- Locate consent and suppression data and treat it as first-class. Losing an opt-out list is a compliance incident, not an inconvenience.
- Agree what 'done' means: record counts, spot checks, and reports that must match.
During the migration
- Dry-run into a staging environment and review the validation report before touching production.
- Import in reversible batches with a rollback plan per batch.
- Freeze or dual-write during cutover so nothing lands only in the old system.
- Keep the old system read-only and accessible until the agreed retention date.