AZ-900 Describe Azure management and governance Practice Question
Which Azure cost optimization practice involves analyzing resource usage and removing or resizing underutilized resources?
⚠ Common exam trap
Many exam-takers confuse 'right-sizing' with 'Reserved Instances' because both reduce costs, but Reserved Instances are a commitment-based discount model, not an analysis-driven resizing practice.
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
✓
Right-sizing underutilized resources
Right-sizing underutilized resources is a core Azure cost optimization practice that involves analyzing resource usage metrics (e.g., CPU, memory, disk I/O) and then either resizing to a smaller SKU or deallocating idle resources. This directly reduces compute, storage, and licensing costs by aligning capacity with actual demand, as opposed to paying for over-provisioned capacity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Reserved Instance purchasing
Why it's wrong here
Reserved Instance purchasing is a pricing and capacity commitment mechanism where you prepay for one or three years of compute capacity in exchange for a discounted hourly rate. While this can reduce overall costs, it does not address the problem of overprovisioned resources; you are still paying for the same large VM size, just at a discounted rate. Right-sizing focuses on matching resource capacity to actual demand, which is a fundamentally different lever. Therefore, reserved instances are not a technique for optimizing the size of existing underutilized resources.
- ✓
Right-sizing underutilized resources
Why this is correct
Right-sizing is a cost optimization practice that uses Azure Advisor and Azure Monitor metrics to identify virtual machines, SQL databases, or App Service plans that are consistently underutilized (e.g., low CPU, memory, or I/O). By resizing these resources to a smaller, appropriately matched SKU or tier, you eliminate waste from overprovisioning while maintaining performance. It directly aligns with the Well-Architected Framework's cost optimization pillar, and unlike other options, it does not involve pre-purchase commitments or altering data replication or disk types.
- ✗
Enabling geo-redundant storage
Why it's wrong here
Enabling geo-redundant storage (GRS) replicates your storage account data asynchronously to a secondary region, providing higher durability and a recovery point objective (RPO) for regional disasters. This replication incurs additional costs for both the duplicate storage capacity and the data transfer to the secondary region, increasing your overall bill. It is a data protection and high-availability feature, not a cost optimization technique. In contrast, right-sizing reduces cost by scaling down unused capacity, whereas GRS deliberately adds cost to meet SLA and compliance requirements.
- ✗
Using Premium SSD disks for all workloads
Why it's wrong here
Using Premium SSD disks for all workloads is an example of overengineering rather than cost optimization. Premium SSDs deliver high IOPS and low latency, which are beneficial for I/O-intensive production databases, but they are unnecessarily expensive for non-critical workloads like development/test servers, log storage, or archival data. Right-sizing would recommend selecting the cheapest acceptable disk tier—such as Standard HDD, Standard SSD, or Ultra Disk based on actual IOPS requirements—for each workload. Applying premium disks uniformly inflates costs without proportional performance benefits, which contradicts the goal of matching resources to real needs.
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