AZ-900 Describe Azure architecture and services Practice Question
A company runs a large data analytics job for a few hours each week. They want to use Azure virtual machines with the lowest possible cost, accepting that the VMs may be reclaimed by Azure at any time. Which pricing option should they choose?
⚠ Common exam trap
Watch out — candidates often confuse Spot VMs with pay-as-you-go, assuming pay-as-you-go is always the cheapest flexible option, but Spot VMs offer a much lower cost specifically for workloads that can handle interruptions.
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
✓
Spot VMs
Spot VMs allow you to use unused Azure compute capacity at a significant discount (up to 90% compared to pay-as-you-go) but can be evicted by Azure when capacity is needed elsewhere. This makes them ideal for interruptible, batch-style workloads like a weekly data analytics job that can tolerate interruptions and resume later.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Spot VMs
Why this is correct
Azure Spot VMs offer a steep discount (up to 90%) compared to pay-as-you-go by using unused Azure capacity, but Azure can evict them when it needs the capacity back. For a large analytics job that runs only a few hours at a time, eviction risk is manageable if the workload is interruptible and can be resumed. This makes Spot VMs the most cost-effective, appropriate choice for this scenario.
- ✗
Reserved Instances
Why it's wrong here
Reserved Instances require a one- or three-year commitment in exchange for a lower hourly rate. Since the analytics job runs for only a few hours at a time and likely not continuously, a long-term reservation would lock you into paying for capacity year-round, even when the job is idle. Spot VMs offer comparable or better savings for intermittent, interruptible workloads without any long-term commitment.
When this WOULD be correct
A company runs a steady-state workload 24/7 for at least one year and wants to reduce costs compared to pay-as-you-go pricing. Reserved Instances would be the correct answer because they offer a significant discount for a long-term commitment.
- ✗
Pay-as-you-go
Why it's wrong here
Pay-as-you-go (PAYG) charges a per-second or per-hour rate with no upfront commitment, but it provides no discount for interruptibility or capacity flexibility. Since the analytics job runs sporadically for a few hours, PAYG would cost far more than Spot VMs because you pay the full rate for every compute hour, even though the workload can tolerate interruption. It is a simple option but not optimized for cost.
When this WOULD be correct
A company needs to run a critical application on Azure VMs 24/7 for the next three years, requires high availability, and cannot tolerate interruptions. Reserved Instances would be the correct answer for cost savings with a long-term commitment.
- ✗
Dedicated Hosts
Why it's wrong here
Dedicated Hosts provide physical servers dedicated entirely to your workloads, offering hardware isolation, control over maintenance, and licensing benefits. However, they are billed per host, not per VM, and you pay for the entire host even when it is underutilized. For a short, occasional analytics job, this is drastically over-provisioned and far more expensive than Spot VMs, so it is not a cost-effective choice.
When this WOULD be correct
A company requires compliance with specific security or licensing policies that mandate dedicated physical servers, and they are willing to pay a premium for full control over the host hardware. For example, a financial institution needing to run a workload on a dedicated server to meet regulatory requirements.
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.
✓Spot VMsCorrect answer▾
Why this is correct
Azure Spot VMs offer a steep discount (up to 90%) compared to pay-as-you-go by using unused Azure capacity, but Azure can evict them when it needs the capacity back. For a large analytics job that runs only a few hours at a time, eviction risk is manageable if the workload is interruptible and can be resumed. This makes Spot VMs the most cost-effective, appropriate choice for this scenario.
✗Reserved InstancesWrong answer — click to see why▾
Why this is wrong here
Reserved Instances require a 1- or 3-year commitment and are not designed for workloads that can be interrupted; they are not suitable for jobs that run only a few hours per week and accept VM reclamation.
★ When this WOULD be the correct answer
A company runs a steady-state workload 24/7 for at least one year and wants to reduce costs compared to pay-as-you-go pricing. Reserved Instances would be the correct answer because they offer a significant discount for a long-term commitment.
Why candidates choose this
Candidates may think Reserved Instances are the cheapest option overall, but they fail to recognize that the workload is short and intermittent, and that Spot VMs offer much lower cost for interruptible workloads.
✗Pay-as-you-goWrong answer — click to see why▾
Why this is wrong here
Pay-as-you-go VMs are not the lowest cost option for interruptible workloads; they incur charges for every hour of usage without the significant discount offered by Spot VMs, and they are not reclaimed by Azure.
★ When this WOULD be the correct answer
A company needs to run a critical application on Azure VMs 24/7 for the next three years, requires high availability, and cannot tolerate interruptions. Reserved Instances would be the correct answer for cost savings with a long-term commitment.
Why candidates choose this
Candidates may think pay-as-you-go is the cheapest because it has no upfront commitment, but they overlook that Spot VMs offer even lower prices for interruptible workloads.
✗Dedicated HostsWrong answer — click to see why▾
Why this is wrong here
Dedicated Hosts provide physical servers dedicated to the customer, which is the most expensive option and does not allow for reclamation by Azure. The question requires the lowest cost with acceptance of VM reclamation, which is the opposite of Dedicated Hosts.
★ When this WOULD be the correct answer
A company requires compliance with specific security or licensing policies that mandate dedicated physical servers, and they are willing to pay a premium for full control over the host hardware. For example, a financial institution needing to run a workload on a dedicated server to meet regulatory requirements.
Why candidates choose this
Candidates may think Dedicated Hosts offer cost savings through isolation or assume that 'dedicated' implies lower cost due to lack of sharing, but they are actually more expensive and not reclaimable.
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.