AZ-305 Design data storage solutions Practice Question
A company needs a fully managed NoSQL database for a new application with a key-value and document data model. They require single-digit millisecond latency at any scale, multi-region writes with automatic conflict resolution, and a serverless capacity option to handle unpredictable traffic. Which Azure data service should they use?
⚠ Common exam trap
Watch out — candidates often confuse Azure Table Storage as a NoSQL database that supports multi-region writes, but it lacks document support and automatic conflict resolution, making Cosmos DB the only option that meets all requirements.
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 both key-value and document data models natively. It guarantees single-digit millisecond latency at any scale, offers multi-region writes with automatic conflict resolution via its multi-master replication, and provides a serverless capacity mode that automatically scales based on demand, making it ideal for unpredictable traffic.
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 stores schemaless entities in a key-value format, but each table is tied to an Azure Storage account that is regional; it offers geo-redundant storage for disaster recovery but does not accept concurrent writes in multiple regions with automatic conflict resolution. It also lacks a true serverless capacity model and cannot consistently deliver the single-digit millisecond latency and 99.999% availability SLA that Cosmos DB provides at global scale.
- ✓
Azure Cosmos DB
Why this is correct
Azure Cosmos DB is the correct choice because it is a fully managed, multi-model NoSQL database that guarantees single-digit millisecond latency for reads and writes at the 99th percentile. Its multi-region writes capability lets you write to any region with automatic conflict resolution policies and a health-based failover, while the serverless mode adds throughput and storage per request, making it ideal for spiky or unpredictable workloads.
- ✗
Azure Cache for Redis
Why it's wrong here
Azure Cache for Redis is an in-memory key-value store optimized for caching, session state, and sub-millisecond lookups; it is not engineered as a durable, system-of-record NoSQL database. Even with optional persistence or the Enterprise tier, it lacks the automatic conflict resolution and natively multi-writer regions of Cosmos DB, and its capacity model is cluster/provisioned rather than fully serverless, so using it as a global multi-writer database risks data loss if nodes fail before persistence.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is a relational database engine with a fixed schema, T-SQL, and rich relational integrity features, not a NoSQL key-value or document store. Its active geo-replication supports a single writer with readable secondary replicas, not multi-region writes with automatic conflict resolution, and its serverless compute option still requires defining a relational schema rather than handling documents or raw key-value items the way Cosmos DB does.
Quick reference
Cloud Service Model Comparison
| Model | You Manage | Provider Manages | Examples |
|---|---|---|---|
| IaaS | OS, runtime, apps, data | Hardware, hypervisor, networking | EC2, Azure VMs, GCP Compute Engine |
| PaaS | Apps and data | OS, runtime, middleware, hardware | Elastic Beanstalk, Azure App Service |
| SaaS | Data and settings only | Everything else | Microsoft 365, Salesforce, Workday |
| FaaS / Serverless | Function code only | Infra, scaling, runtime | Lambda, Azure Functions, Cloud Run |
| CaaS | Containers and apps | Kubernetes, OS, hardware | EKS, AKS, GKE |
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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.