Describe considerations for working with non-relational data on Azure →easyMultiple ChoiceObjective-mapped
DP-900 Practice Question: Describe considerations for working with non-relational data on Azure
A startup is building a mobile app that requires offline data synchronization. The app needs to store user-generated content locally on the device and sync with Azure when connectivity is available. Which Azure service should they use for the cloud backend?
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
✓
Azure Cosmos DB
Azure Cosmos DB is the correct choice because it supports offline data synchronization through its Mobile Apps SDK, allowing mobile apps to store data locally and sync with Azure when connectivity is available. Azure Blob Storage (Option B) lacks built-in offline sync for mobile apps. Azure SQL Database (Option C) is relational and not optimized for offline sync scenarios. Azure Table Storage (Option D) does not provide robust offline sync capabilities.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is the correct choice because the Azure Mobile Apps SDK provides first-class offline data sync for Cosmos DB as the backend. The SDK embeds a local SQLite cache on the device, tracks all pending create, update, and delete operations, and automatically reconciles them with the cloud when connectivity returns. It also supports multi-master writes with conflict-resolution policies, such as last-write-wins or custom resolution, making it uniquely suited for a mobile app that must function offline and re-sync later.
- ✗
Azure Blob Storage
Why it's wrong here
Azure Blob Storage is an object store designed for unstructured data like images, videos, and backups, not for application-defined records that change over time. It has no built-in offline sync engine, no client-side change tracking, and no automatic conflict resolution, so a mobile app would need to implement its own local caching and manual upload logic from scratch. Moreover, Blob Storage charges and organizes data by blob names and containers, making it impractical for a mobile app requiring transparent offline CRUD operations.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is a relational database that emphasizes transactional consistency and requires an active connection for every query operation; it does not natively provision a local cache on the mobile device. While Azure SQL offers geo-replication, that is server-side availability for disaster recovery, not offline synchronization for disconnected clients. The Azure Mobile Apps SDK historically can use SQL Database as a backend, but offline sync support is provided by the client SDK's sync layer, not by the database itself, and the underlying SDK has been deprecated in favor of Azure Data API Builder with different offline capabilities.
- ✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is a NoSQL key-value store designed for semi-structured data at massive scale, but it lacks any built-in mobile offline sync primitives. There is no SDK component that maintains a local pending-operations queue, no conflict-resolution policy definition, and no change-feed mechanism suitable for throttled pull-based synchronization. A developer would need to write custom logic to track row versions, compare ETags across devices, and merge updates manually, which makes it far less suitable than Cosmos DB for this offline-first mobile app.
Visual reference
Quick reference
Azure Blob Storage Tier Comparison
| Tier | Storage Cost | Retrieval Cost | Latency | Use Case |
|---|---|---|---|---|
| Hot | Highest | Lowest | Immediate | Active data, frequent reads |
| Cool | Lower | Higher | Immediate | Data accessed < once / month |
| Cold | Lower still | Higher | Immediate | Data accessed < once / quarter |
| Archive | Lowest | Highest + rehydration delay | Hours | Long-term compliance retention |
Go deeper
Related to this question
Learn chapter
Data Roles and Core Concepts
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
Key term
Blob storage
Blob storage is a cloud service for storing large amounts of unstructured data, such as text or binary data, like documents, images, and videos.
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