AZ-900 Describe Azure architecture and services Practice Question
A company manages 50 Azure SQL Databases, each used by a different department. Each database experiences low average usage (less than 5 DTU on average) but unpredictable hourly peaks that can reach up to 50 DTU for short bursts. The company wants to minimize total cost while ensuring every database can handle its peak load without performance degradation. Which Azure SQL Database deployment option should the company choose?
⚠ Common exam trap
It's easy for candidates to choose the single database with 50 DTU (Option B) because they focus on the peak requirement (50 DTU) without considering the cost inefficiency of provisioning each database for its maximum, missing the elastic pool's ability to share resources and reduce total cost.
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 SQL Database elastic pool
Azure SQL Database elastic pool is the correct choice because it allows multiple databases to share a fixed pool of DTU resources, enabling the aggregated peak loads to be handled efficiently without over-provisioning each database individually. With low average usage (less than 5 DTU) but unpredictable bursts up to 50 DTU, an elastic pool provides the necessary headroom for spikes while minimizing total cost by only paying for the pooled eDTUs, not per-database maximums.
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 elastic pool
Why this is correct
Correct. An elastic pool allows multiple databases to share a pool of resources (DTUs or vCores). Each database can burst up to the pool's limit, accommodating peak loads cost-effectively because the pooled resources are larger than any single database's average but smaller than the sum of all peaks.
- ✗
Azure SQL Database single database with 50 DTU
Why it's wrong here
Incorrect. A single database with 50 DTU provisioned for each of the 50 databases would be extremely expensive because most of the time the databases use only 5 DTU. The cost would be far higher than an elastic pool while not providing additional benefit.
When this WOULD be correct
This option would be correct if the company had only one or a few databases with consistent peak loads near 50 DTU, and the cost of over-provisioning a single database was acceptable. For example, a mission-critical database with steady high usage would justify a single database with reserved DTU.
- ✗
Azure SQL Managed Instance
Why it's wrong here
Incorrect. Azure SQL Managed Instance offers instance-level compatibility and is optimized for migrations from on-premises SQL Server. It does not provide the granular resource-sharing model of elastic pools for many small databases. It would be overprovisioned and more costly for this use case.
When this WOULD be correct
A company needs to migrate multiple on-premises SQL Server databases to Azure with minimal application changes, requiring features like SQL Server Agent, cross-database queries, and instance-level collation. They have a few large databases with steady workloads and require high compatibility.
- ✗
SQL Server on an Azure virtual machine
Why it's wrong here
Running SQL Server on an Azure VM requires the customer to manage the operating system, SQL Server patches, and scaling decisions manually, which contradicts the stem’s need for each of 50 databases to handle unpredictable bursts to 50 DTU without performance degradation—the VM’s fixed compute resources cannot elastically scale per database, whereas a serverless or DTU-based Azure SQL Database would auto-scale. This option is tempting because it offers full control over SQL Server configuration and is correct when the company requires custom SQL Server features, legacy compatibility, or OS-level access that a managed service cannot provide.
When this WOULD be correct
A company needs full control over the SQL Server configuration, including custom features, third-party tools, or legacy applications that require OS-level access. They are willing to manage the VM to avoid compatibility issues with PaaS offerings.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓Azure SQL Database elastic poolCorrect answer▾
Why this is correct
Correct. An elastic pool allows multiple databases to share a pool of resources (DTUs or vCores). Each database can burst up to the pool's limit, accommodating peak loads cost-effectively because the pooled resources are larger than any single database's average but smaller than the sum of all peaks.
✗Azure SQL Database single database with 50 DTUWrong answer — click to see why▾
Why this is wrong here
Choosing a single database with 50 DTU for each of 50 databases would be far more expensive than an elastic pool, as each database is provisioned for peak DTU even though average usage is low, leading to significant over-provisioning and cost.
★ When this WOULD be the correct answer
This option would be correct if the company had only one or a few databases with consistent peak loads near 50 DTU, and the cost of over-provisioning a single database was acceptable. For example, a mission-critical database with steady high usage would justify a single database with reserved DTU.
Why candidates choose this
Candidates may think that provisioning each database at its peak DTU (50 DTU) guarantees performance without understanding that elastic pools allow sharing of resources across databases with low average usage and unpredictable peaks, reducing total cost.
✗Azure SQL Managed InstanceWrong answer — click to see why▾
Why this is wrong here
Azure SQL Managed Instance is designed for lift-and-shift migrations with near 100% SQL Server compatibility, not for managing many small databases with variable loads. It does not provide the elastic pooling feature to share resources across databases, making it cost-inefficient for this scenario.
★ When this WOULD be the correct answer
A company needs to migrate multiple on-premises SQL Server databases to Azure with minimal application changes, requiring features like SQL Server Agent, cross-database queries, and instance-level collation. They have a few large databases with steady workloads and require high compatibility.
Why candidates choose this
Candidates may confuse Managed Instance with elastic pool, thinking it offers similar resource sharing, or assume 'managed' implies automatic scaling for multiple databases, overlooking that it's a single-instance deployment without built-in pooling.
✗SQL Server on an Azure virtual machineWrong answer — click to see why▾
Why this is wrong here
SQL Server on an Azure VM requires manual patching, backups, and high availability setup, increasing operational overhead and cost. It does not provide the automated scaling and shared resource pooling of an elastic pool, making it unsuitable for 50 low-usage databases with unpredictable peaks.
★ When this WOULD be the correct answer
A company needs full control over the SQL Server configuration, including custom features, third-party tools, or legacy applications that require OS-level access. They are willing to manage the VM to avoid compatibility issues with PaaS offerings.
Why candidates choose this
Candidates may think running SQL Server on a VM offers more flexibility and lower cost for many databases, but they overlook the management overhead and the fact that elastic pools are designed specifically for such multi-database scenarios with variable usage patterns.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 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-900 exam.