Open Data Infrastructure
How to Migrate Data Platforms Without Downtime
Dual-write, parallel-run validation, and reversible cutovers for migrations that cannot break production.
“No downtime” migrations are not a heroic engineering feat. They are a design constraint that forces you to treat reversibility as part of the architecture.
The principle
A downtime-free migration is one where the old and new systems can both serve the workload during a transition period, and where rollback is a normal operational procedure.
If rollback is not possible, you do not have “no downtime.” You have “we hope this works.”
Core idea: reversibility is the control plane for migrations.
Parallel runs
Parallel running means running the same workload on both systems and comparing outputs while production continues.
- Start with a small set of representative queries and pipelines.
- Expand coverage as confidence grows, including edge cases.
- Define which differences are acceptable and which indicate semantic drift.
- Log and analyze differences so you learn, not so you argue.
Parallel runs are slow. That is the point. They surface the hidden assumptions that big-bang plans skip.
Dual-write strategies
Dual-write is writing to both the old and new platforms during a transition window. It is useful when:
- The workload is mission critical.
- Data freshness matters.
- You cannot tolerate loss during the cutover.
Dual-write has risks. The two systems can diverge. If you adopt dual-write, you also need a reconciliation strategy and a clear ownership model.
Validation that earns trust
Validation is not one check. It is a ladder:
- Structural parity: schemas, partitions, and expected record counts.
- Content parity: sampling-based checksums and domain-specific invariants.
- Query parity: representative workloads and performance behavior.
- Governance parity: permissions, audit logs, and lineage coverage.
Teams lose time when they skip directly to query parity without defining the invariants that matter.
A reversible cutover
A reversible cutover has three properties:
- Clear routing control: you can route consumers to old or new without code archaeology.
- Data safety windows: you can replay or reconcile data written during the transition.
- Operational runbooks: rollback steps are tested before you need them.
ODI helps here because open contracts reduce the number of system-specific rewrite steps. The fewer proprietary dependencies you have, the easier reversible cutovers become.
Sources to start with
For ODI migrations, the durable contract layer is grounded in table and catalog specs and portable lineage.