Data residency.
Not just a location.

Residency: where do the bytes sit? Which physical data centre, in which country. This is what regional cloud endpoints answer, and it is the question most procurement processes ask.

Jurisdiction: who can compel access? A provider incorporated in one country operating a data centre in another may be subject to lawful access requests from the first. That is the question behind sovereign cloud initiatives, and it is a legal question rather than a technical one — but the technical architecture determines how much it matters.

Access: who can actually reach it? Which engineers, under what controls, with what logging, from where. A provider with support staff in several regions has a different access surface from a single-tenant machine in your building, regardless of where either sits.

Answering only the first and treating the other two as covered is a common gap in AI vendor assessments. They are separate questions with separate answers, and an AI system — which concentrates data from across the organisation — is precisely where the difference starts to matter.

We start by asking which of the three questions your requirement is actually about, because the answer changes the architecture substantially and the requirement as written is often ambiguous. “Data must stay in the EU” is satisfiable by a regional endpoint; “no non-EU entity may be able to compel access” is not, and the two frequently appear in the same policy document.

Then we design so the constraint is structural rather than contractual. A model running on hardware you own, with no egress route, cannot transmit data anywhere — which is stronger than any contractual assurance and considerably easier to evidence. Where a hosted path is acceptable, we pin the region, document the provider's position and make the data flows explicit in the architecture record.

And we write down what leaves. For every system we build, a diagram showing which data crosses which boundary, to whom, under what agreement. That document is what a DPO, an auditor or an enterprise customer's security team actually needs, and producing it as part of the build is far cheaper than reconstructing it under time pressure.