Question 338 of 964
PCD Integrating Google Cloud services Practice Question
You are designing a serverless application using Cloud Functions that processes events from Cloud Storage and Cloud Pub/Sub. The function must be idempotent and handle duplicate events. Which three best practices should you implement? (Choose THREE.)
⚠ Common exam trap
Many exam-takers confuse timeout settings or synchronous invocation with duplicate prevention, but neither addresses the root cause of duplicate events from at-least-once delivery systems. In Google Cloud, Cloud Functions may receive duplicate events from Cloud Storage notifications or Pub/Sub, making idempotency keys and state tracking essential.
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
✓
Generate a unique idempotency key for each event and store processed keys in a database.
Generating a unique idempotency key for each event and storing processed keys in a database (such as Cloud Firestore) ensures that if the same event is delivered multiple times (e.g., due to at-least-once delivery semantics in Cloud Pub/Sub or Cloud Storage notifications), the function can check the key before processing and skip duplicates. This pattern is essential for idempotent serverless functions, as Cloud Functions may be retried on failure or receive duplicate events from the source.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Generate a unique idempotency key for each event and store processed keys in a database.
Why this is correct
Idempotency keys prevent duplicate processing.
- ✗
Invoke the function synchronously to avoid duplicates.
Why it's wrong here
Synchronous invocation is not supported for background functions.
- ✓
Implement a deduplication logic that checks the event's publish time against a threshold.
Why this is correct
Timestamps can help filter duplicates.
- ✓
Use Cloud Firestore to record the state of each processed event.
Why this is correct
Transactional state helps idempotency.
- ✗
Set the function timeout to maximum (540 seconds) to ensure processing completes.
Why it's wrong here
Timeout does not prevent duplicates.
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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Last reviewed: Jun 11, 2026
This PCD 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 PCD exam.
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