AZ-305 Design data storage solutions Practice Question
You need to design a storage solution for a global e-commerce application that requires low-latency access to product catalog data across multiple Azure regions. The data is read-heavy and updates are rare. Which service should you use for the primary data store?
⚠ Common exam trap
It's easy for candidates to confuse a caching layer (Redis) with a globally distributed primary store, or assume that a relational database with geo-replication (Azure SQL) is suitable for any multi-region scenario, ignoring the specific read-heavy, rare-update pattern that Cosmos DB is optimized for.
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 globally distributed, multi-region writes and reads with turnkey data replication and guaranteed single-digit-millisecond latency at the 99th percentile. Its multi-homing API and automatic failover capabilities make it ideal for a read-heavy, rarely updated global e-commerce catalog that requires low-latency access across multiple Azure 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 SQL Database with active geo-replication
Why it's wrong here
Azure SQL Database with active geo-replication is not ideal because it maintains a single writable primary; the geo-replicated replicas are read-only, and failover to a secondary requires a manual or automated but still non-transparent change of the database role. In a global e-commerce workload with writes originating from many regions, all write requests must be routed to the primary region, adding cross-region network latency, and asynchronous replication means the secondary can lag, risking data loss during an unplanned outage. It does not provide the turnkey, multi-master global distribution that the scenario requires.
- ✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is a key-value/NoSQL store that, by default, is scoped to a single region for writes; geo-redundant storage can place a read-only copy in a paired region, but only for high availability or disaster recovery, not for active global write distribution. Requests from users in other continents still travel to the primary region for write operations, so latency is poor for a truly global, write-heavy e-commerce store. It also lacks Cosmos DB's tunable consistency and multi-master write capability across any number of Azure regions.
- ✗
Azure Redis Cache
Why it's wrong here
Azure Redis Cache is an in-memory data store designed for caching, not as a durable source of truth; although Redis can persist to disk with AOF/RDB, the Azure Cache for Redis service is not built for multi-region active-active writes and does not provide transactional guarantees or conflict-resolution protocols needed for e-commerce order data. If a cache node fails or the service restarts, you can lose recent writes or still need to rebuild from another database, making it unsuitable for the canonical storage layer. Using Redis would add performance but not solve global durability and availability.
- ✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is the correct choice because it provides turnkey global distribution with the ability to add any number of read and write regions around the world, and it offers multiple well-defined consistency levels that let you balance strong consistency and low latency per request. Each region is fully manageable, writes are accepted anywhere and conflict resolution can be configured to handle concurrent updates, giving single-digit millisecond latencies while maintaining high availability through automatic failover. This makes it a natural fit for a global e-commerce platform that needs fast, reliable access from anywhere.
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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.