Google ACE Planning and Configuring a Cloud Solution Practice Question
A team is building a mobile app backend that requires real-time data synchronization across devices and offline support. The data model is simple and document-based. Which database service should they use?
⚠ Common exam trap
ACE often tests the distinction between Firestore and Firebase Realtime Database; candidates might confuse the two, but Firestore is the newer, more scalable option with richer querying 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 document database that provides real-time synchronization and offline support for mobile and web applications. It is designed for mobile app backends with simple document-based data models, offering automatic scaling and strong consistency. Firestore's real-time listeners and offline persistence make it ideal 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 database designed for large-scale analytical and operational workloads, offering very low latency and high throughput at the cost of a tightly coupled connection to a managed VPC. It has no client-side SDK for mobile apps, no built-in real-time synchronization, and no offline data persistence, so it cannot support the real-time sync and offline-first requirements of a mobile app backend.
- ✗
BigQuery
Why it's wrong here
BigQuery is a serverless, highly scalable data warehouse built for running SQL analytics on petabyte-scale datasets, not for powering transactional or real-time mobile app backends. It has high latency for point reads and writes, does not provide real-time listeners or client-side offline caching, and its cost model makes frequent small updates prohibitively expensive and architecturally inappropriate.
- ✗
Cloud SQL
Why it's wrong here
Cloud SQL is a managed relational database that provides ACID transactions and full SQL semantics, but it has no native mobile client SDKs or built-in real-time synchronization capabilities. Mobile clients would need to open direct connections and implement custom polling or WebSocket logic, and offline persistence would require manual local caching and complex conflict resolution, making it a poor fit for real-time sync scenarios.
- ✓
Firestore
Why this is correct
Firestore is a flexible, scalable NoSQL document database designed natively for mobile app development, with real-time listeners that push data changes to clients instantly and offline data persistence that automatically syncs when connectivity returns. Its client SDKs for iOS, Android, and web handle multi-device synchronization, conflict resolution, and data integrity out of the box, making it the ideal choice for this real-time mobile backend use case.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
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.