PrivateLink interface endpoints: verify DNS and traffic

A private endpoint changes the service request path

An interface VPC endpoint exposes a supported service through private network interfaces in selected subnets. Applications can often keep using the service's normal Regional hostname when private DNS is configured correctly. That convenience depends on name resolution and network access working together.

The presence of an endpoint is not evidence that a workload uses it. A custom resolver can still return public addresses, or the application can use a different Region or hostname. Establish the exact request before editing routing or granting broader permissions.

Setup and prerequisites

Record the workload VPC, service name, Region, endpoint ID, selected subnets and interface addresses. Check that the endpoint type matches the service and intended architecture; gateway endpoints, interface endpoints and resource endpoints have different contracts.

For private DNS, verify both VPC DNS resolution and DNS hostnames settings. Map custom DNS forwarding back to the supported VPC resolver path. Identify endpoint security groups, workload egress policy, network ACLs and the service action required by the application.

Inspect the request in four steps

1. Resolve the actual service hostname from the affected workload. Compare returned addresses with the endpoint network interfaces. A successful lookup from an administrator laptop does not describe the workload resolver.
2. Test the required transport path using the authorized destination and port. Inspect the endpoint security group's inbound rules and the workload's outbound controls. Include return traffic where stateless network ACLs apply.
3. If transport works but the API denies access, inspect the endpoint policy and the runtime IAM identity. Endpoint policy is an additional boundary; it does not replace the service's identity and resource policies.
4. Compare failing and working Availability Zones and subnets. Check which endpoint interfaces exist and which address the client selected before attributing the problem to a whole Region.

Illustrative incident: a private subnet still uses public DNS

In this illustrative scenario, an application loses access after its NAT path is removed. An interface endpoint already exists, but a custom DNS forwarding rule resolves the AWS service hostname outside the VPC's private DNS context. The application continues trying the public path.

The operator verifies the returned addresses, repairs the reviewed resolver forwarding configuration and repeats the same API request with the same workload role. The example demonstrates path diagnosis and does not claim a measured customer outage or cost saving.

Diagnostic table

Correction and verification

Repair the evidenced DNS, security-group or policy condition with the narrowest required change. Preserve the previous resolver configuration and working administration path. Do not treat public service access as the only valid fallback if the architecture requires a private boundary.

Verify a representative service operation from each relevant workload location. Confirm that the chosen hostname resolves through the intended path, the operation succeeds with the intended identity and unrelated actions remain denied. Include the service's own dependencies when planning an endpoint-only environment.

Monitoring and SOP

Document service and endpoint identities, DNS ownership, interface placement and permission owners. Monitor application API failures and collection freshness alongside network evidence. A conceptual endpoint diagram helps troubleshooting, but the SOP should retain actual DNS responses and request errors so future subnet or resolver changes can be validated against observed behavior.

See Clouvenix cloud architecture for implementation and operational handover.

Technical reference

Official reference 1; Official reference 2. Documentation checked 20 October 2026; confirm behavior for your deployed edition and version.