Measure the real bottleneck
Migration speed is often constrained by a combination of source queries, transformation work, network throughput, target writes and coordination overhead.
Measure every stage before increasing parallelism; otherwise, concurrency can amplify contention.
Tune in layers
Optimize SQL access paths, reduce unnecessary data movement, partition work into balanced units and automate repeatable execution. Each layer should be measurable and independently recoverable.
Design for restartability
A fast migration that cannot restart safely is operationally expensive. Track progress at a durable unit of work and make partial retries predictable.