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Google ACE Practice Question: A developer receives a "Permission…
A developer receives a "Permission 'cloudfunctions.functions.call' denied" error when trying to invoke a Cloud Function from another service. What is the most likely cause?
⚠ Common exam trap
Google Cloud often tests the distinction between IAM permission errors and network/configuration errors, so candidates mistakenly choose CORS or VPC options because they think invocation failures are always due to networking or browser restrictions, but the specific error message points directly to a missing IAM role.
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 of the caller lacks the Cloud Functions Invoker role.
The error 'Permission cloudfunctions.functions.call denied' indicates that the Identity and Access Management (IAM) policy does not grant the caller the required permission to invoke the function. The Cloud Functions Invoker role (roles/cloudfunctions.invoker) specifically allows the `cloudfunctions.functions.call` permission, which is necessary for HTTP-triggered functions. Without this role on the caller's service account, any invocation attempt will be denied, regardless of other configurations.
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 service account of the caller lacks the Cloud Functions Invoker role.
Why this is correct
Cloud Functions enforces IAM authorization at the time of invocation: the caller's identity (a user or service account) must hold the roles/cloudfunctions.invoker role on the function. If that binding is missing, the Cloud Functions API responds with HTTP 403 Permission Denied even though the function exists and is healthy. This is the standard failure when a service account is used for authentication without explicitly granting the invoker role.
- ✗
The function is not deployed to the correct region.
Why it's wrong here
If the function were deployed to a region different from the one in the request URL, the regional endpoint would report the resource as not found, producing a 404 'function not found' error rather than a permission denied. The error text in the question is an IAM authorization failure that occurs after the request reaches the correct function resource. A region mismatch affects URL routing and resource discovery, not access-control evaluation.
- ✗
The Cloud Function has a CORS misconfiguration.
Why it's wrong here
CORS misconfigurations are enforced by the web browser on the client side, causing preflight failures or blocked cross-origin requests in the browser console; they never generate a server-side HTTP 403 IAM permission denied response from Cloud Functions. Moreover, the permission error indicates that the HTTP request actually reached Cloud Functions and was evaluated by its IAM policy layer. CORS only affects how browsers interpret responses that Cloud Functions successfully returned.
- ✗
The VPC connector is not configured correctly.
Why it's wrong here
A misconfigured VPC connector in Cloud Functions affects outbound network access between the function and resources in a VPC network, typically resulting in connection timeouts or inability to resolve private IPs when the function itself initiates egress traffic. It does not alter how incoming HTTP invocation requests are authenticated or authorized by Cloud Functions' IAM system. Therefore, an IAM permission denied error cannot be explained by a VPC connector configuration issue.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
Go deeper
Related to this question
Learn chapter
Cloud Functions (1st and 2nd Gen)
Key term
IAM
Identity and Access Management (IAM) is a framework of policies and technologies that ensures the right individuals have the appropriate access to technology resources.
Key term
Service account
A service account is a special type of account used by an application or a virtual machine, rather than a human user, to authenticate and interact with cloud services and APIs securely.
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This ACE question is part of Courseiva's 775-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ACE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the ACE exam.