DP-900 Describe core data concepts Practice Question
You need to design a data storage solution for a global e-commerce application that must support ACID transactions and require minimal latency for point lookups by a unique key. Which Azure data service should you use?
⚠ Common exam trap
A common mix-up: candidates assume Azure SQL Database is the only ACID-compliant option, overlooking Cosmos DB's transactional batch support and its superior global low-latency capabilities.
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 provides global distribution with multi-region writes, guarantees ACID transactions through its transactional batch API, and offers single-digit millisecond latency for point reads by a unique key (e.g., id and partition key). This makes it ideal for a global e-commerce application requiring both strong consistency and low-latency lookups.
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 Table Storage
Why it's wrong here
Azure Table Storage is a NoSQL key-value store that supports limited atomic operations per entity or per partition via entity group transactions, but it lacks the full cross-partition ACID transactions required for complex business logic. Moreover, while it offers geo-redundant storage, it does not provide single-digit millisecond point-read latency with multiple consistency models and multi-region write support that Cosmos DB does for a globally distributed e-commerce application.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database provides full ACID compliance and a relational model, but it is designed as a single-region primary database; for global deployments, cross-region readers use asynchronous geo-replication, so write latency is tied to the primary region. This makes it impractical for a high-velocity global e-commerce application that requires low-latency writes and reads in multiple regions simultaneously, which is why Cosmos DB is the preferred choice for global point-lookup workloads.
- ✗
Azure Blob Storage
Why it's wrong here
Azure Blob Storage is optimized for storing massive volumes of unstructured data such as documents, images, and backups, with a flat object store accessed via HTTP. It does not expose a query engine for transactional point lookups, does not support multi-item ACID operations, and its access latency is higher than a high-throughput NoSQL database, making it unsuitable for a product-catalog or order lookup service.
- ✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is a globally distributed, multi-model NoSQL database that offers turnkey distribution across any number of Azure regions, multi-region write support, and single-digit millisecond read and write latencies at the 99th percentile. It also guarantees ACID transactions within a single logical partition using transactional batches or stored procedures, making it the right fit for a global e-commerce platform that needs both low-latency point lookups and data consistency.
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.