Relay is a pattern for proxying a request to a third-party API without exposing the underlying credential to the application runtime. The worker sends its own identity and the target URL, and the relay service injects the provider credential upstream. This reduces token handling in untrusted environments while preserving auditability.
Expanded Definition
Relay is an NHI security pattern that separates request initiation from credential presentation. Rather than letting an application runtime hold a provider secret, the worker sends the relay service its own identity plus the destination endpoint, and the relay injects the upstream credential on behalf of that request. This is especially useful when the worker runs in an untrusted or heavily shared environment where secrets would otherwise be exposed in memory, logs, or build artifacts.
In practice, relay sits between direct API calls and broader gateway or broker designs. Its main purpose is not traffic shaping, but controlled credential mediation, auditable access, and reduced token handling. That makes it relevant to service accounts, API keys, certificates, and short-lived tokens in agentic workflows. Definitions vary across vendors on how much authorization logic belongs in the relay itself versus the calling workload, so teams should treat relay as an access-control pattern rather than a universal proxy architecture. For governance context, see the NIST Cybersecurity Framework 2.0 and NHIMG’s Ultimate Guide to NHIs.
The most common misapplication is treating a relay as a generic reverse proxy, which occurs when teams forward arbitrary requests without binding them to a verified worker identity or target-specific policy.
Examples and Use Cases
Implementing relay rigorously often introduces an extra trust decision point, requiring organisations to weigh simpler application code against tighter policy enforcement and additional latency.
- A CI/CD job needs to call a cloud storage API. The job sends its workload identity to the relay, and the relay injects the provider credential only for the approved bucket action.
- An AI agent invokes a third-party ticketing API. The relay checks the agent’s scoped identity, then substitutes a short-lived token so the agent never handles the provider secret directly.
- A microservice running in a shared Kubernetes cluster accesses an external payment API. The relay centralises credential use while keeping the service runtime free of long-lived secrets.
- A vendor integration is allowed to read status data but not issue changes. The relay enforces target-specific rules so the same application cannot reuse the credential for broader access.
- For broader NHI governance patterns, NHIMG’s Ultimate Guide to NHIs is useful when paired with the identity and access concepts in the NIST Cybersecurity Framework 2.0.
Why It Matters in NHI Security
Relay matters because it reduces the blast radius of credential exposure. If an application runtime never receives the upstream secret, attackers who compromise the workload have less to steal and less to reuse. That directly supports least privilege, secret containment, and clearer audit trails, especially where service accounts and API keys are used across agentic systems. It also helps teams avoid the common anti-pattern of embedding long-lived credentials in application code or configuration, a problem NHIMG research shows is still widespread.
NHIMG reports that 96% of organisations store secrets outside of secrets managers in vulnerable locations including code, config files, and CI/CD tools. Relay is one practical way to shrink that exposure surface, but only when it is paired with strong identity verification, scoped authorization, and rotation discipline. It should also be considered alongside the control objectives in the NIST Cybersecurity Framework 2.0, especially where credential misuse can lead to lateral movement or unauthorized API access. Organisations typically encounter the operational necessity of relay only after a secret leak, at which point the pattern becomes unavoidable to contain repeat exposure.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Non-Human Identity Top 10 and CSA MAESTRO address the attack and risk surface, while NIST CSF 2.0, NIST Zero Trust (SP 800-207) and NIST SP 800-63 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Non-Human Identity Top 10 | NHI-02 | Relay reduces secret exposure, a core improper secret management concern. |
| NIST CSF 2.0 | PR.AC | Relay supports authenticated, policy-driven access to external services. |
| NIST Zero Trust (SP 800-207) | SC-3 | Relay aligns with zero trust by verifying identity before granting access. |
| NIST SP 800-63 | AAL2 | Relay depends on strong assertion of the worker identity that initiates access. |
| CSA MAESTRO | Agentic workflows often need mediated credential use rather than direct secret handling. |
Keep provider secrets out of worker runtimes and enforce relay-mediated upstream access.
Related resources from NHI Mgmt Group
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Reviewed and updated by the NHIMG editorial team on August 23, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
