What breaks first when you move ISO market data to the cloud

Cloud migrations of ISO market-data platforms rarely stumble on raw compute. Storage and horsepower are the easy part — you can buy as much as you want. They stumble on the quiet assumptions the old environment absorbed invisibly: feed timing, late-arriving revisions, and the reconciliation logic that lived in a job nobody documented. Move the data and leave those assumptions behind, and the platform runs fine while producing numbers the desk no longer trusts.

What actually breaks, roughly in order

• Feed timing and ordering. ISO postings arrive on their own cadence, and a lot of downstream logic silently depended on when files landed relative to each other. Lift it into a new orchestration layer and the ordering assumptions surface as intermittent, hard-to-reproduce gaps.
• Late-arriving revisions. Settlement data is restated. If the old pipeline quietly reprocessed a day when the ISO reissued it, and the new one appends instead of corrects, history starts drifting from the operator’s version.
• Undocumented reconciliation. The check that made everyone trust the numbers — the one that tied the platform back to the ISO statement — is often the least documented step, because it “just worked.” It’s also the first thing whose absence gets noticed.
• Identity and lineage. Nodes, zones, and instruments get remapped in migration; if the keys shift, a chart that looks right is aggregating the wrong things.

Sequence the move so trust survives it

The way through is to treat trust in the numbers as the thing being migrated, not the bytes. Stand the new platform up in parallel, run both against the same feeds, and reconcile the new output against the old — and against the ISO’s own statements — before anything downstream cuts over. Make the timing, revision, and reconciliation rules explicit in the new pipeline rather than implicit in the old one, so the assumptions become code you can test instead of folklore you rediscover in production.

Compute is the part of an ISO market-data migration you can buy your way through. The trust in the numbers is the part you have to migrate deliberately — and it’s the only part the desk will actually notice if you get it wrong.