AZ-305 Design data storage solutions Practice Question
A global e-commerce company uses Azure Cosmos DB to store its product catalog. The catalog is read-heavy, with users worldwide expecting consistent reads with a 99th percentile latency under 10 ms. Writes to the catalog are performed by a central admin team in one region. The company needs to minimize write latency and cost while ensuring that users always see the same data within a single session. Which Cosmos DB configuration should the company choose?
⚠ Common exam trap
Test-takers frequently confuse 'strong consistency' with 'always correct' and overlook that Session consistency is sufficient for per-session guarantees, while Strong consistency adds unnecessary latency and cost for a read-heavy catalog with centralized writes.
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
✓
Single-master write region with Session consistency and multiple read regions
Session consistency provides the required 'read your own writes' guarantee within a single session, which ensures users always see the same data during their session without the latency and cost penalties of Strong consistency. Single-master writes minimize write latency by directing all writes to one region (the central admin team's region), while multiple read regions allow global users to read from the nearest region with sub-10 ms latency. This configuration balances cost, performance, and consistency needs for a read-heavy catalog with centralized writes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Single-master write region with Strong consistency and multiple read regions
Why it's wrong here
A single-master write region with strong consistency requires every write to be synchronously replicated to all read regions before acknowledging the client, so write latency scales with the distance to the farthest region and can be significantly higher than necessary. This configuration also reduces write availability because if any read region is unreachable or unhealthy, writes cannot be committed, risking availability during a partial regional outage. Since the application only needs per-user session consistency, strong consistency is an unnecessary and costly over-provisioning that does not align with the global e-commerce reading pattern, where reads dominate and writes are localized.
- ✗
Multi-master write with Eventual consistency and all regions enabled for writes
Why it's wrong here
Enabling all regions for writes (multi-master) is unjustified because the application receives writes from only one region, so a single write region avoids the need for conflict-resolution logic and reduces operational cost. Eventual consistency, without session tokens, cannot guarantee that a user reads the data they just wrote within the same session; they might see stale or conflicting data as reads are served from different regions. This directly violates the explicit session consistency requirement while adding unnecessary write-write conflict handling, higher complexity, and no tangible benefit for a workload with a single write location.
- ✓
Single-master write region with Session consistency and multiple read regions
Why this is correct
Session consistency deployed with a single-master write region and multiple read regions is the optimal balance: all writes are sent to one regional endpoint, minimizing write latency and avoiding cross-region conflict resolution. The Cosmos DB SDK manages session tokens to ensure that within the same user session, reads are served from any read region yet still reflect the most recent writes performed in that session, satisfying the requirement for session consistency. This design provides low-latency reads globally for the e-commerce workload, where users access the application from various geographic regions, without the cost or complexity of multi-master writes.
- ✗
Multi-master write with Strong consistency and two regions
Why it's wrong here
This configuration is invalid in Azure Cosmos DB because strong consistency is not supported when multiple write regions are enabled; the service only allows strong consistency with a single write region, making a multi-master strong-consistency topology technically impossible. Even if it were possible, combining strong consistency with multi-master would force every write to be synchronously replicated across all regions before acknowledgment, which eliminates the latency benefits of multi-master writes and significantly increases both write latency and RU consumption. Since writes originate from only one region and the application only requires session consistency, this approach is overkill, unsupported, and not aligned with the stated requirements.
Go deeper
Related to this question
About these practice questions
This AZ-305 question is part of Courseiva's 212-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
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.