AZ-305 Design business continuity solutions Practice Question
You are designing a business continuity solution for a globally distributed SaaS application that uses Azure Cosmos DB for its operational store. The application must survive a complete regional outage with zero data loss and automatic failover. What should you use?
⚠ Common exam trap
Test-takers frequently assume multi-region writes (Option C) are necessary for zero data loss, but they overlook that multi-region writes require eventual consistency and conflict resolution, which can lead to data loss or conflicts, whereas a single write region with strong consistency and automatic failover provides the strictest guarantee of zero data loss.
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
✓
Configure Cosmos DB with a single write region, strong consistency, and enable automatic failover to a secondary region.
It combines a single write region with strong consistency and automatic failover, which guarantees zero data loss during a regional outage. Strong consistency ensures that all reads reflect the latest write, and automatic failover allows Azure to promote a secondary read region to the primary write region without manual intervention, meeting the requirement for zero data loss and automatic failover.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure a single write region in Cosmos DB with eventual consistency and manual failover.
Why it's wrong here
Manual failover with eventual consistency cannot guarantee zero data loss because the secondary replica may not have received all recent writes. Eventual consistency means replication is asynchronous, so any un-replicated transactions would be lost, yielding an RPO greater than zero. Additionally, requiring manual action to trigger failover increases RTO, as the recovery depends on human intervention rather than automated detection and response.
- ✓
Configure Cosmos DB with a single write region, strong consistency, and enable automatic failover to a secondary region.
Why this is correct
Strong consistency in Azure Cosmos DB ensures that all reads return the most recently committed write, and with a single write region, writes are synchronously replicated to the secondary region before acknowledgment. This guarantees an RPO of zero because no acknowledged data is lost during a regional outage. Enabling automatic failover allows Cosmos DB to detect a region failure and redirect traffic without manual intervention, thereby satisfying the required RTO target.
- ✗
Enable multi-region writes in Cosmos DB with eventual consistency and automatic failover.
Why it's wrong here
Configuring multiple write regions with eventual consistency sacrifices the ability to achieve zero data loss because each region accepts and acknowledges writes independently, then replicates asynchronously. If a region fails before its pending writes are propagated, those writes are permanently lost, resulting in an RPO greater than zero. Furthermore, Azure Cosmos DB does not support strong consistency when multiple write regions are enabled, so this configuration cannot provide the required strong consistency guarantee.
- ✗
Use Azure SQL Database with active geo-replication and automatic failover.
Why it's wrong here
Azure SQL Database with active geo-replication is the wrong choice here because the application's operational data store is Azure Cosmos DB, not SQL Database. Even if SQL Database were considered, active geo-replication uses asynchronous data replication, which typically provides an RPO of up to 5 seconds, so it cannot meet the strict zero data loss requirement. The failover process for SQL Database also involves a different set of constraints and does not offer the same global distribution and consistency models that Azure Cosmos DB provides.
Go deeper
Related to this question
Learn chapter
Designing Governance Solutions
Key term
Cosmos DB Design
Cosmos DB Design is the process of structuring data and choosing configuration settings in Azure Cosmos DB to ensure fast performance, low cost, and scalability for applications.
Key term
Azure Site Recovery
Azure Site Recovery is a Microsoft Azure service that keeps your business applications and data running by automatically replicating them to a secondary location and failing over if the primary site goes down.
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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.