Gateway policy governs request flow, identity context, budgets, and tool access. Data-store permissions govern which documents or records can be returned once the request reaches a vector store or search system. Both are needed, but they operate at different layers and should not be merged into one control.
Why gateway policy and data-store permissions belong on different layers
Gateway policy is the front door control. It decides whether a request is allowed to proceed at all, based on factors such as identity context, request shape, tenant rules, rate limits, budgets, and which tools or routes the caller may use. Data-store permissions sit deeper in the retrieval path, deciding which indexed documents, chunks, rows, or records can actually be returned after the request reaches search or vector infrastructure.
That separation matters because a gateway can approve a request without authorising every possible object the backend could surface. Likewise, a datastore can safely filter results even when the request itself is valid. Treating them as the same control usually creates either excessive exposure or broken functionality, because one layer is built to govern request movement and the other is built to govern data visibility.
In practice, gateway policy is about per-action authorisation, while datastore permissions are about retrieval-time access to the underlying content. The first layer should stop an unauthorised caller, tool, or agent from reaching a protected capability. The second layer should stop a valid caller from seeing records it should not receive even after the request is accepted.
What each control prevents in a retrieval flow
Gateway policy prevents unsafe requests from ever becoming active work. It can block over-broad tools, enforce tenant isolation, require approval for sensitive actions, cap usage, and apply identity-aware conditions before downstream systems are invoked. It is also the right place to apply request-level guardrails when a caller is acting on behalf of a human or another system.
Data-store permissions prevent over-disclosure after the request is already valid. They govern whether a query can return a document, row, passage, embedding-derived result, or other object based on the requesting identity and the object’s own access rules. This is especially important in search and retrieval systems, where the backend can easily surface material the caller was never meant to see if filtering is done too late or too loosely.
Permission-aware retrieval is the clearest example of why the backend layer still needs its own rules: if permissions are only checked at the gateway, a well-formed query can still over-retrieve once it reaches the index or vector store. The backend must enforce document-level or record-level visibility, not assume the front door already solved the problem.
How to split responsibility without creating gaps
Gateway policy should own request admission, route selection, and the boundaries around what a caller is allowed to ask a system to do. Data-store permissions should own object-level visibility, so the answer set is trimmed to what the caller may actually receive. When those duties are blended, teams often end up with a single broad allow/deny rule that is too weak for retrieval security and too rigid for request governance.
- Use the gateway to decide whether the request, tool call, or query is permitted to proceed.
- Use the datastore to decide which objects, chunks, or records may be returned.
- Keep identity context consistent across both layers so the backend can enforce the same subject that the gateway evaluated.
- Review both layers together when you see oversharing, because fixing only one often leaves the other path open.
That split is also why authorisation models matter here: gateway checks usually align with coarse policy decisions, while datastore controls often need finer-grained object rules. The control boundary should be explicit, otherwise teams tend to grant the gateway too much power and the datastore too little context.
Risk and Threat Considerations
The main risk is assuming that a successful request at the gateway means the data returned is safe. In retrieval systems, that mistake can expose documents across teams, tenants, or sensitivity tiers even when the front door looked correct. It also creates a tempting abuse path for attackers or over-privileged callers, because they only need one layer to be weaker than the other.
Failure mechanism: The gateway permits the query or tool call, but the datastore returns objects without applying the correct object-level filter, so the caller receives more content than intended.
Impact: Sensitive records can leak through search, vector, or RAG-style retrieval, and the blast radius is often larger than expected because the same flawed pattern can repeat across many queries and many identities.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP API Security Top 10 and OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST SP 800-53 Rev 5 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP API Security Top 10 | API5 — Broken Function Level Authorization | Gateway policy concerns whether a caller may invoke a function or tool route. |
| API1 — Broken Object Level Authorization | Data-store permissions control which records or documents may be returned to a caller. | |
| Recommendation — Enforce function-level checks before allowing sensitive routes or tool actions. Apply object-level checks on every retrieval, not just at the gateway. | ||
| NIST SP 800-53 Rev 5 | AC-6 — Least Privilege | Both layers should limit callers to the minimum request and data access needed. |
| IA-9 — Identification and Authentication (Service Accounts and Workloads) | Retrieval systems and gateways depend on trustworthy non-human caller identity context. | |
| Recommendation — Restrict request paths and returned data to the minimum necessary privilege. Authenticate service-to-service calls so backend permissions map to the real caller. | ||
| OWASP Non-Human Identity Top 10 | NHI-05 — Overprivileged NHI | Gateway and datastore separation prevents a non-human caller from gaining broader access than intended. |
| Recommendation — Right-size non-human access at both the request and data layers. | ||
Practitioner Guidance
What to verify: Confirm that the gateway and datastore each make an independent decision, and that the datastore is not trusting a gateway assertion as a substitute for object-level access control. If the backend cannot prove which identity it evaluated, the design is too loose for sensitive retrieval.
Common mistake: Teams often harden the gateway and stop there. That improves admission control, but it does not prevent over-retrieval, which is why search and vector systems should be tested with queries that are valid at the edge but unauthorized at the object layer.
Practitioner takeaway: The right design is layered, not duplicated, the gateway decides whether a request may proceed, and the datastore decides what content may be returned once it does.
Related resources from NHI Mgmt Group
- What is the difference between privilege reduction and secret rotation?
- What is the difference between a rules-based secret scanner and a hybrid scanner?
- What is the difference between code scanning and runtime identity monitoring?
- What is the difference between zero trust for users and zero trust for NHIs?