PDE Storing the Data Practice Question
A startup is building a mobile app that needs to sync user data across devices in real time. They expect millions of concurrent users and need a NoSQL database with offline support and automatic multi-region replication. Which Google Cloud service meets these requirements?
⚠ Common exam trap
A common mix-up: candidates confuse Cloud Spanner's global SQL capabilities with NoSQL requirements, or assume Cloud Bigtable's NoSQL label fits all NoSQL workloads, ignoring the specific need for real-time sync and offline support.
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
✓
Firestore
Firestore is a NoSQL, serverless document database that provides real-time synchronization, offline support via local persistence, and automatic multi-region replication. It is designed for mobile and web apps with millions of concurrent users, making it the ideal choice for this use case.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Cloud Bigtable
Why it's wrong here
Cloud Bigtable is a wide-column NoSQL store for high-throughput analytical and time-series workloads, but it provides no offline sync SDK, no automatic multi-region replication, and no mobile client library. It is tempting because it handles millions of concurrent operations, and would be correct for large-scale telemetry or IoT data at low latency.
- ✗
Cloud Spanner
Why it's wrong here
Cloud Spanner is a strongly consistent, horizontally scalable relational database with SQL and schemas, not NoSQL; its multi-region replication is synchronous, adding write latency unsuitable for real-time mobile sync. It is tempting because Spanner scales globally to millions of users, and would be correct for a globally distributed transactional workload needing relational consistency.
- ✓
Firestore
Why this is correct
Firestore provides a serverless NoSQL document store with built-in offline persistence via client SDKs and automatic multi-region replication, directly satisfying the real-time sync, offline support and global scale constraints. Its real-time listeners push updates across devices, meeting the millions-of-concurrent-users requirement.
- ✗
Cloud SQL
Why it's wrong here
Cloud SQL is a regional relational engine without native offline sync or multi-region NoSQL replication, so it cannot serve millions of concurrent mobile clients. It is tempting for familiar SQL workloads and small managed databases, but Firestore or Bigtable provide the offline support and automatic multi-region replication required here.
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
About these practice questions
One of 747 original PDE practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PDE 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 PDE exam.