Azure Cosmos DB with strong consistency is the correct choice because it uniquely enables multi-region writes with strong consistency, allowing an active-active configuration where every region can accept writes while guaranteeing that all reads return the most recent write globally. This is achieved through a synchronous replication protocol that ensures linearizability across regions, delivering fractional millisecond latency for single-digit KB payloads by using direct connectivity and optimized routing. On the AZ-305 exam, this scenario tests your understanding of the trade-offs between consistency models and global distribution; a common trap is assuming that multi-region writes inherently sacrifice strong consistency, but Cosmos DB’s strong consistency mode explicitly supports this when you accept the write latency penalty of synchronous replication. Remember the memory tip: “Strong writes sync globally” — if the question demands both multi-region writes and strong consistency, Cosmos DB is the only Azure data service that delivers both, unlike SQL Database or Azure Cache for Redis which lack active-active strong consistency.
AZ-305 Design data storage solutions Practice Question
This AZ-305 practice question tests your understanding of design data storage solutions. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are designing a solution for a financial application that requires strong consistency for read and write operations across multiple Azure regions. The solution must support active-active configuration and provide fractional millisecond latency for single-digit KB payloads. Which data service should you choose?
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 with strong consistency
Azure Cosmos DB with strong consistency is the correct choice because it offers multi-region writes (active-active) with guaranteed strong consistency, ensuring that all read and write operations across regions see the most recent write. It also provides fractional millisecond latency for single-digit KB payloads, meeting the financial application's performance requirements.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 failover groups
Why it's wrong here
Failover groups provide only active-passive configuration.
✗
Azure Table Storage with geo-replication
Why it's wrong here
Geo-replication provides eventual consistency, not strong.
✓
Azure Cosmos DB with strong consistency
Why this is correct
Cosmos DB supports multi-region writes with strong consistency and low latency.
Related concept
Read the scenario before looking for a memorised answer.
✗
Azure Cache for Redis with geo-replication
Why it's wrong here
Redis is a cache, not a durable database with strong consistency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Azure SQL Database's failover groups with active-active capability, but failover groups are active-passive and cannot support simultaneous writes across regions, whereas Cosmos DB's multi-region writes with strong consistency are required for true active-active scenarios.
Detailed technical explanation
How to think about this question
Cosmos DB's strong consistency model uses multi-master replication with a quorum-based commit protocol (e.g., Paxos) to ensure linearizability across all regions, meaning any read returns the latest write globally. For single-digit KB payloads, Cosmos DB achieves sub-10ms latency at P99 by using direct TCP connectivity and optimized indexing, making it suitable for latency-sensitive financial transactions. In real-world scenarios, this ensures that a balance transfer initiated in one region is immediately visible in another, preventing double-spend or stale reads.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-305 question in full detail.
Design data storage solutions — This question tests Design data storage solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Azure Cosmos DB with strong consistency — Azure Cosmos DB with strong consistency is the correct choice because it offers multi-region writes (active-active) with guaranteed strong consistency, ensuring that all read and write operations across regions see the most recent write. It also provides fractional millisecond latency for single-digit KB payloads, meeting the financial application's performance requirements.
What should I do if I get this AZ-305 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You are designing a data storage solution for a healthcare application that stores patient records. The solution must meet compliance requirements that data in the US must be stored in US regions, and data in the EU must be stored in EU regions. Additionally, the solution must support global queries with low latency. What should you use?
hard
A.Azure Blob Storage with RA-GRS storage accounts in each region
B.Azure SQL Database with active geo-replication and a failover policy
✓ C.Azure Cosmos DB with multi-region writes and conflict resolution policy based on region
D.Azure SQL Managed Instance with failover groups
Why C: Azure Cosmos DB with multi-region writes is the correct choice because it provides active-active replication across multiple regions, enabling low-latency global queries by allowing writes and reads from any region. The conflict resolution policy based on region ensures that data sovereignty requirements are met by prioritizing writes from the region where the data originates (e.g., US writes win in US regions, EU writes win in EU regions), which aligns with the compliance requirement that data must stay within its respective geographic boundary.
Variation 2. You are designing a globally distributed application that requires low-latency reads and writes for a web application with user session data. The solution must support multi-master writes and provide 99.999% availability. Which Azure data service meets these requirements?
medium
A.Azure SQL Database
✓ B.Azure Cosmos DB
C.Azure Cache for Redis
D.Azure Table Storage
Why B: Azure Cosmos DB is the correct choice because it natively supports multi-master writes across multiple regions, enabling low-latency reads and writes globally. It offers a 99.999% availability SLA when configured with multiple write regions, and its turnkey global distribution ensures user session data is replicated with consistency options tailored for web applications.
Variation 3. You are designing a storage solution for a globally distributed application that requires low-latency read access from multiple regions. Which Azure storage solution should you recommend?
easy
A.Azure Blob Storage with read-access geo-redundant storage (RA-GRS)
B.Azure SQL Database with active geo-replication
C.Azure Files with Azure File Sync
✓ D.Azure Cosmos DB with multi-region writes and multiple read regions
Why D: Azure Cosmos DB with multi-region writes and multiple read regions is the correct choice because it provides turnkey global distribution with single-digit-millisecond latency for reads and writes from any Azure region. This solution directly addresses the requirement for low-latency read access from multiple regions, as Cosmos DB automatically replicates data to all configured regions and offers multiple consistency models to balance performance and data freshness.
Variation 4. A globally distributed application requires multi-region writes to a NoSQL database and must tolerate regional write outages. Which Azure service capability should be selected?
hard
A.Azure Table Storage RA-GRS
B.Azure SQL Database serverless only
✓ C.Azure Cosmos DB multi-region writes
D.Azure Files geo-redundant storage
Why C: Azure Cosmos DB multi-region writes is the correct choice because it provides active-active replication across multiple Azure regions, enabling writes to be accepted in any configured region and automatically replicated. This design ensures that if one region experiences a write outage, the application can continue writing to other regions without interruption, meeting the requirement for multi-region writes and regional write outage tolerance.
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Question Discussion
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