Cloud Digital Leader Google Cloud Products and Services Practice Question
A developer needs to trigger a serverless function whenever a new file is uploaded to a Cloud Storage bucket. The function will process the file and store results in Firestore. Which Google Cloud service should they use for the function?
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
✓
Cloud Functions
Cloud Functions is an event-driven serverless compute service that can be triggered by Cloud Storage events.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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App Engine
Why it's wrong here
App Engine is a fully managed platform for building web applications and APIs, not a lightweight event-driven function service. It requires deploying a complete application runtime (e.g., a web framework) and is designed for sustained HTTP traffic, not for triggering code directly on low-level GCP resource events such as a Cloud Storage object finalize. While App Engine can handle background work via task queues or cron, it lacks the native, fine-grained event source integration that Cloud Functions provides for storage events, making it unnecessarily complex and not the correct serverless trigger mechanism for this use case.
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Compute Engine
Why it's wrong here
Compute Engine provides virtual machines that require ongoing management, operating system maintenance, and manual scaling, none of which align with the serverless trigger requirement for Cloud Storage uploads. It is tempting because it can run arbitrary code and process files, but it lacks the native event-driven integration that Cloud Functions offers. Compute Engine would be correct for a long-running application needing full control over the runtime environment.
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Cloud Run
Why it's wrong here
Cloud Run is incorrect because it is primarily designed for stateless containers invoked by HTTP requests or Pub/Sub messages, not directly by Cloud Storage object finalisation events. While a Pub/Sub notification could bridge this, Cloud Functions offers native integration for such event-driven triggers. Cloud Run is tempting as a flexible serverless container platform, ideal for web services, APIs, or background jobs requiring custom runtimes and longer execution times, where an HTTP endpoint or Pub/Sub subscription is the primary invocation method.
- ✓
Cloud Functions
Why this is correct
Cloud Functions is a purpose-built, event-driven serverless compute platform that natively responds to GCP events, including Cloud Storage object finalization (e.g., the 'google.storage.object.finalize' trigger). When an object is uploaded, Cloud Functions automatically invokes the function with the event metadata, scaling to zero when idle and managing all infrastructure transparently. This aligns exactly with the requirement to trigger a single-purpose serverless function on a storage event, without needing a container runtime, a web server, or an intermediary like Pub/Sub.
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 |
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Related to this question
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Cloud Digital Transformation
Key term
Google Cloud
Google Cloud is a suite of cloud computing services offered by Google that provides infrastructure, platform, and software solutions over the internet.
Key term
Serverless function
A serverless function is a single-purpose piece of code that runs in the cloud only when triggered, without you managing any servers.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This GCDL 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 GCDL exam.