AZ-305 Design data storage solutions Practice Question
A company stores JSON documents for a mobile app backend. The data needs to be accessible from multiple global regions with low latency writes from any region. The app uses a client-side library that supports automatic conflict resolution for concurrent updates. Which Azure data service should they choose?
⚠ Common exam trap
Watch out — candidates often confuse Azure SQL Database or Azure Database for PostgreSQL's read replicas with write capability, failing to recognize that only Cosmos DB offers true multi-region writes with built-in conflict resolution.
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 correct because it provides multi-region writes with automatic conflict resolution, which directly matches the requirement for low-latency writes from any global region. Its multi-master replication model allows any region to accept writes, and the client-side library can use last-writer-wins (LWW) or custom conflict resolution policies to handle concurrent updates seamlessly.
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 the correct choice because it provides native multi-region writes, enabling the same JSON document to be written and updated from any Azure region with automatic conflict resolution to handle concurrent edits. Its flexible schema and JSON-native indexing make it purpose-built for storing and querying mobile app backend documents, and it offers well-defined consistency levels and an SLA for availability and latency.
- ✗
Azure SQL Database
Why it's wrong here
Azure SQL Database is incorrect because, although it offers active geo-replication, the secondary replicas are read-only and cannot accept write transactions; only the primary region can serve as the write endpoint. Automatic failover can promote a secondary, but that maintains a single-write-region architecture rather than true multi-region writes, so it does not satisfy the requirement.
- ✗
Azure Database for PostgreSQL
Why it's wrong here
Azure Database for PostgreSQL is unsuitable because its read replicas are asynchronous and operate under a single-master model, with all write operations constrained to the primary server. The service lacks built-in multi-master support and automatic conflict resolution, so distributing write traffic across regions would require custom application logic or third-party extensions.
- ✗
Azure Table Storage
Why it's wrong here
Azure Table Storage is not appropriate for this workload because it is a schema-less key-value store rather than a JSON document database, offering limited querying and no native support for nested JSON properties or automatic conflict resolution. While you could serialize JSON strings into entities, you would sacrifice native JSON indexing and document-level operations, and multi-region writes require custom conflict-handling code.
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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.