- A
Azure SQL Database Hyperscale
Why wrong: Hyperscale separates compute and storage for a large single database but still has a single primary for writes, limiting write scalability.
- B
Azure Cosmos DB
Why wrong: Cosmos DB is a NoSQL database; although it supports SQL querying, it does not provide a relational model with full cross-node join capabilities and transactions.
- C
Azure Database for PostgreSQL Hyperscale (Citus)
Citus distributes data across multiple nodes, allowing horizontal scaling for write-heavy workloads. It supports full SQL, joins, and transactions, meeting the relational database requirements.
- D
Azure SQL Managed Instance
Why wrong: SQL Managed Instance is a single instance version of SQL Server in Azure; it does not natively distribute data across multiple nodes for write scaling.
Quick Answer
The answer is Azure Database for PostgreSQL Hyperscale (Citus) because it is the only fully managed relational database in Azure that natively supports horizontal scaling for write-intensive workloads through the Citus extension, which shards data across multiple worker nodes and parallelizes SQL queries, including complex joins and distributed transactions. On the AZ-305 exam, this scenario tests your ability to distinguish between scaling approaches: Azure SQL Database offers vertical scaling and read scale-out, while Hyperscale (Citus) is specifically designed for high write throughput and elastic scaling across nodes. A common trap is choosing Azure Cosmos DB, which is NoSQL and lacks full relational SQL support, or Azure SQL Database Hyperscale, which scales storage and reads but not write capacity horizontally. Remember the memory tip: “Citus splits writes across nodes—think ‘Citus’ as ‘Cuts’ the data into shards for high write throughput.”
AZ-305 Design data storage solutions Practice Question
This AZ-305 practice question tests your understanding of design data storage solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
A company runs a large-scale write-intensive application that requires a horizontally scalable relational database. They need to distribute data across multiple nodes to handle high write throughput while supporting SQL queries, including joins and transactions. The solution must be fully managed and provide elastic scaling. Which Azure database service should they choose?
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 Database for PostgreSQL Hyperscale (Citus)
Azure Database for PostgreSQL Hyperscale (Citus) is the correct choice because it provides horizontal scaling (sharding) across multiple worker nodes using the Citus extension, which distributes data and parallelizes SQL queries. It supports full SQL, including joins and transactions, while offering elastic scaling for write-intensive workloads. This makes it ideal for large-scale relational databases that need high write throughput and horizontal scalability.
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 Hyperscale
Why it's wrong here
Hyperscale separates compute and storage for a large single database but still has a single primary for writes, limiting write scalability.
- ✗
Azure Cosmos DB
Why it's wrong here
Cosmos DB is a NoSQL database; although it supports SQL querying, it does not provide a relational model with full cross-node join capabilities and transactions.
- ✓
Azure Database for PostgreSQL Hyperscale (Citus)
Why this is correct
Citus distributes data across multiple nodes, allowing horizontal scaling for write-heavy workloads. It supports full SQL, joins, and transactions, meeting the relational database requirements.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Azure SQL Managed Instance
Why it's wrong here
SQL Managed Instance is a single instance version of SQL Server in Azure; it does not natively distribute data across multiple nodes for write scaling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'horizontal scaling' with 'hyperscale' or 'managed instance' options, assuming any 'scalable' database service supports distributed writes, but only Citus provides true horizontal sharding for relational workloads with full SQL and transaction support.
Detailed technical explanation
How to think about this question
Citus achieves horizontal scaling by using a coordinator node that distributes data across worker nodes based on a distribution column (shard key). Queries are automatically parallelized across workers, and distributed transactions are supported via two-phase commit (2PC) with PostgreSQL's native transaction support. In real-world scenarios, this is critical for SaaS applications with multi-tenant databases where each tenant's data is sharded across nodes to handle millions of writes per second while maintaining ACID compliance.
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
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Design data storage solutions — study guide chapter
Learn the concepts, then practise the questions
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Design data storage solutions practice questions
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FAQ
Questions learners often ask
What does this AZ-305 question test?
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 Database for PostgreSQL Hyperscale (Citus) — Azure Database for PostgreSQL Hyperscale (Citus) is the correct choice because it provides horizontal scaling (sharding) across multiple worker nodes using the Citus extension, which distributes data and parallelizes SQL queries. It supports full SQL, including joins and transactions, while offering elastic scaling for write-intensive workloads. This makes it ideal for large-scale relational databases that need high write throughput and horizontal scalability.
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.
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Last reviewed: Jun 11, 2026
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.
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