AZ-305 Design data storage solutions Practice Question
A global e-commerce company runs a product catalog application that requires low-latency reads and writes from multiple geographic regions. The data is key-value structured and must be replicated with multi-region write capability. The company needs a fully managed NoSQL database service with guaranteed 99th percentile latency and automatic conflict resolution. Which Azure data service should they choose?
⚠ Common exam trap
Many exam-takers confuse Azure Table Storage's NoSQL nature with Cosmos DB's multi-region write and latency guarantees, overlooking the critical requirements for automatic conflict resolution and 99th percentile latency SLAs.
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 is a fully managed NoSQL database that supports multi-region writes with automatic conflict resolution, guarantees 99th percentile latency, and provides low-latency reads and writes globally. Its multi-master replication and tunable consistency models meet the key-value structured data requirements and the need for high availability across geographic regions.
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 a globally distributed NoSQL database engineered for product-catalog workloads that require active-active writes across multiple Azure regions. It supports a choice of APIs (SQL, MongoDB, Cassandra, etc.), and with multi-region writes it provides automatic conflict resolution, turnkey global distribution, and deterministic 99th-percentile latency SLAs. For an ecommerce catalog, Cosmos DB's partition-key design and tunable consistency levels allow low-latency reads and writes at scale while meeting a strict SLO.
- ✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is a NoSQL key-value service, but its replication pairs a single write region with asynchronously replicated read-only secondary geo-replication; it does not support multi-region writes, so active-active catalog updates are impossible. It also offers no 99th-percentile latency guarantee and no automatic conflict resolution, making it an acceptable low-cost store for non-critical data rather than a globally distributed catalog backend.
- ✗
Azure Redis Cache
Why it's wrong here
Azure Redis Cache is an in-memory data structure server, so although it can deliver response times in microseconds, it is not a persistent primary database and loses data on failover unless AOF/RDB persistence is explicitly configured. It does not provide multi-region write replication or automatic conflict resolution, and caching a catalog would require an underlying durable store such as Cosmos DB. As a cache, it cannot serve as the deterministic, globally consistent source of truth for product inventory and pricing.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is a relational engine and can geo-replicate a catalog, but its active geo-replication and auto-failover groups only permit a single primary write region; read secondaries are read-only and cannot accept writes. It is not a NoSQL service, so the flexible schema required by heterogeneous product attributes would force multiple BLOB/JSON mappings, and its latency SLA is not a 99th-percentile deterministic guarantee like Cosmos DB. Therefore it is a strong OLTP relational choice, not the best fit for globally distributed ecommerce catalog writes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 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 AZ-305 exam.