DP-900 Describe core data concepts Practice Question
A startup is building a mobile app that allows users to share short text updates. Each update includes a user ID, timestamp, and message text. The development team expects rapid growth and needs a storage solution that can scale horizontally, handle high write throughput, and provide low-latency reads globally. Which Azure data service is most appropriate?
⚠ Common exam trap
A common mix-up: candidates confuse Azure Table Storage's horizontal scaling with the global, multi-master capabilities of Cosmos DB, assuming Table Storage can provide low-latency writes worldwide when it lacks native multi-region write support and has higher latency for cross-region 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 with a multi-master configuration and partition on user ID.
Azure Cosmos DB with a multi-master configuration is the most appropriate choice because it provides global distribution with multiple write regions, enabling horizontal scaling and low-latency reads and writes worldwide. Partitioning on user ID ensures even data distribution and efficient query performance for the app's high write throughput requirements.
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 SQL Database with a single database.
Why it's wrong here
Azure SQL Database as a single database is a relational store with fixed compute/storage limits (DTU/vCore) and a single write region. It cannot offer active multi-region writes or single-digit millisecond latency globally; geo-replication is asynchronous and designed for disaster recovery, not for low-latency writes from a globally distributed mobile audience. A relational schema also imposes rigid overhead for simple short-text posts at very high ingest rates.
- ✓
Azure Cosmos DB with a multi-master configuration and partition on user ID.
Why this is correct
Azure Cosmos DB with multi-master configuration and partition on user ID is correct because it provides active-active multi-region writes, 99.999% availability, and tunable consistency with single-digit millisecond latencies at the 99th percentile. Using user ID as the partition key co-locates all posts from one user on the same logical partition, enabling efficient queries and scalable writes. Multi-master lets users write to the nearest region while Cosmos DB reconciles conflicts, which is exactly what a high-throughput, globally distributed short-text app needs.
- ✗
Azure Blob Storage with append blobs.
Why it's wrong here
Azure Blob Storage with append blobs treats each short text post as a binary append operation, but Blob Storage is optimized for large, immutable objects, not for high-frequency small writes or queryable records. Append blobs are designed for sequential append-only logs; reading or indexing individual messages would require scanning the blob, and concurrent appends to a single blob create a serialization bottleneck. There is no partition-key-based querying or sub-millisecond lookup for individual text items, making it impractical for a social feed.
- ✗
Azure Table Storage with user ID as partition key and timestamp as row key.
Why it's wrong here
Azure Table Storage with user ID as partition key and timestamp as row key gives a reasonable NoSQL key-value design for ordering a user's posts, but it lacks built-in multi-region writes and active-active global distribution. Table Storage supports geo-redundancy only for failover scenarios, not concurrent writes from multiple regions with conflict resolution, so users far from the primary region would experience higher write latency. It also provides limited secondary indexing and no tunable consistency options, making it weaker than Cosmos DB for a latency-sensitive global short-text service.
Go deeper
Related to this question
Learn chapter
Data Roles and Core Concepts
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.
Key term
Data
Data is raw, unprocessed information, like numbers, words, or measurements, that can be stored, processed, and analyzed by computers.
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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.