Legacy Data Migration Strategy
Google Cloud's own migration guidance states the constraint every cut-over plan has to accept: genuinely zero downtime is impossible. This guide works through the decision a legacy data migration actually turns on, big bang against outbox-based trickle against log-based change data capture, why a dual write without a transactional outbox can silently diverge two databases, reconciliation tiered from row counts to field-level checks and the rehearsal and rollback discipline AWS's own cutover guidance describes.