PDE Storing the Data Practice Question
A mobile app needs a NoSQL database that supports offline synchronization when the device goes offline and later reconnects. Which Google Cloud database should be used?
⚠ Common exam trap
The trap is confusing Firestore with other NoSQL databases like Bigtable, or assuming that Spanner's global distribution supports offline sync, when only Firestore provides native offline synchronization for mobile apps.
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 built-in offline synchronization for mobile and web apps. It caches data locally and automatically syncs changes when the device reconnects, making it ideal for offline-capable applications.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Firestore
Why this is correct
Firestore is a NoSQL document database with built-in offline persistence: the client SDK caches data locally and synchronises changes automatically when connectivity returns. This directly satisfies the stem's offline synchronisation constraint, unlike Cloud SQL or Bigtable, which lack native mobile offline support.
- ✗
Cloud Bigtable
Why it's wrong here
Bigtable is a wide-column store for high-throughput analytics and time-series data, with no client-side offline cache or sync API, so a disconnected mobile app cannot queue and reconcile writes. It would suit petabyte-scale IoT or ad-tech ingestion, not mobile sync.
- ✗
Cloud Spanner
Why it's wrong here
Spanner is a globally distributed relational database offering strong consistency and SQL, not a document store with device-side offline caching and conflict resolution. It fits horizontally scaled, globally consistent transactional workloads rather than intermittently connected mobile clients.
- ✗
Cloud SQL
Why it's wrong here
Cloud SQL is a relational engine, so it lacks the schemaless document model and built-in mobile synchronisation layer the app requires. It would be the right pick for a transactional application needing SQL joins and ACID guarantees, not offline-capable NoSQL.
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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 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.