DP-900 Describe core data concepts Practice Question
You need to choose a data store for a mobile app that requires real-time synchronization of user preferences across devices. The data is small per user and key-value oriented. Which Azure service is most appropriate?
⚠ Common exam trap
Many candidates confuse Azure Cache for Redis as a primary data store for persistent, synchronized user preferences, overlooking its transient nature and lack of built-in conflict resolution for multi-device scenarios.
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 most appropriate choice because it provides global distribution, low-latency reads and writes, and automatic conflict resolution, which are essential for real-time synchronization of user preferences across devices. Its key-value API (e.g., Table API or Core SQL API with a simple partition key) efficiently handles small, per-user data with a key-value orientation, ensuring that changes made on one device are quickly reflected on others.
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 correct because it is a globally distributed, multi-model NoSQL database that provides a key-value API along with single-digit-millisecond read and write latency, which directly satisfies a mobile app's need for fast, scalable access. It also offers SDKs for iOS and Android, turnkey global distribution, and multiple consistency levels, enabling low-latency access from any region and supporting offline or sync-based scenarios.
- ✗
Azure Cache for Redis
Why it's wrong here
Azure Cache for Redis is wrong because it is an in-memory cache rather than a durable, authoritative data store; data is held primarily in RAM and can be lost on service restart, failover, or eviction due to memory pressure. It is meant to sit in front of a database for hot data and accelerate reads, not to serve as the system of record for a mobile application, so it cannot be the primary data store.
- ✗
Azure Blob Storage
Why it's wrong here
Azure Blob Storage is wrong because it is designed for massive unstructured objects like images, videos, backups, and log files, not for small, frequently updated key-value records that a mobile app must read and write individually. Its REST API is object- and container-oriented, lacks native key-value semantics or fine-grained querying, and would introduce excessive latency and operational complexity for simple, per-user application data.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is wrong because it requires a fixed relational schema and carries relational overhead such as ACID transactions, indexing, and join processing, which is overkill for a simple key-value data requirement. While it can deliver low latency, it is harder to scale transparently across many regions and to adapt to rapidly changing mobile app fields compared to a purpose-built NoSQL key-value store like Cosmos DB.
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
Service
A service is a software component or system that performs a specific function and is available to be used by other programs or users over a network.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DP-900 practice question is part of Courseiva's free Microsoft 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 DP-900 exam.