Troubleshooting Dataflow Permission Denied: Granting iam.serviceAccountUser for Cross-Project Access

A company uses multiple GCP projects and wants to allow a service account from Project A to initiate Dataflow jobs in Project B. The service account in Project A has the Dataflow Developer role at the organization level. However, it fails with permission denied when trying to submit a job to Project B. What is the most likely issue?

Quick Answer

The answer is that the service account from Project A needs the Service Account User role (roles/iam.serviceAccountUser) on the Dataflow service account in Project B. This is required because when a Dataflow job is submitted to a target project, the job executes under the identity of a service account in that project, not the caller’s identity. The caller must have the `iam.serviceAccounts.actAs` permission on that target service account to delegate their authority; without it, the API call fails with a “dataflow cross project permission denied” error, even if the caller holds the Dataflow Developer role at the organization level. On the Google Professional Cloud Security Engineer exam, this scenario tests your understanding of the separation between job submission permissions and execution identity permissions—a common trap is assuming that broad roles like Dataflow Developer automatically grant cross-project `actAs` rights. Remember the memory tip: “Developer lets you submit, but Service Account User lets you act as.”

⚠ Common exam trap

Google Cloud often tests the distinction between having a role that grants the ability to create a resource (like Dataflow Developer) versus the need for the Service Account User role to act as the service account that runs the resource, which is a subtle but critical IAM permission requirement.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The service account needs the Service Account User role on the Dataflow service account in Project B.

The service account from Project A has the Dataflow Developer role at the organization level, which grants permissions to create Dataflow jobs, but it still needs the Service Account User role (roles/iam.serviceAccountUser) on the Dataflow service account in Project B. When a Dataflow job is submitted, the job runs as a service account in the target project (Project B), and the caller must have the iam.serviceAccounts.actAs permission on that service account. Without this role, the API call fails with a permission denied error even though the Dataflow Developer role is present.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The organization policy restricts cross-project access.
Why it's wrong here
Organization policies would affect all projects, not just cross-project.
✗
The service account does not have permission to create Dataflow jobs in Project B because it is not a member of Project B.
Why it's wrong here
Organization-level roles grant access across all projects, so membership isn't the issue.
✗
The Dataflow API is not enabled in Project B.
Why it's wrong here
If the API were disabled, the error would be different.
✓
The service account needs the Service Account User role on the Dataflow service account in Project B.
Why this is correct
To act as the project's compute service account, the launching service account needs roles/iam.serviceAccountUser.

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Same concept, more angles

1 more way this is tested on PCSE

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. A Dataflow job launched by service account 'my-sa@...' fails with permission denied. The audit log shows the above entry. What missing role is causing the failure?

medium

A.roles/iam.workloadIdentityUser on the worker service account
✓ B.roles/iam.serviceAccountUser on the worker service account
C.roles/iam.serviceAccountAdmin on the worker service account
D.roles/iam.serviceAccountTokenCreator on the worker service account

Why B: When a Dataflow job fails with permission denied and the audit log shows the entry, the missing role is typically roles/iam.serviceAccountUser on the worker service account. This role is required because the Dataflow service (or the service account launching the job) must be able to impersonate the worker service account to execute the pipeline's tasks. Without this role, the job cannot assume the identity of the worker service account, leading to the permission denied error.

Last reviewed: Jun 30, 2026

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