AZ-900 Describe Azure architecture and services Practice Question
Which Azure compute option is BEST for a batch processing job that can tolerate interruptions and needs the lowest possible compute cost?
⚠ Common exam trap
Watch out — candidates often confuse Azure Spot VMs with Azure Reserved Instances, assuming reserved pricing is always the cheapest, but they fail to recognize that Spot VMs offer even lower costs for workloads that can handle interruptions, which is the key differentiator in this scenario.
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 Spot VMs
Azure Spot VMs are designed for interruptible workloads like batch processing jobs that can tolerate preemption. They offer the lowest compute cost by leveraging unused Azure capacity, with discounts of up to 90% compared to pay-as-you-go pricing, making them the optimal choice for cost-sensitive, fault-tolerant tasks.
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 Reserved VM Instances
Why it's wrong here
Azure Reserved VM Instances require a one- or three-year commitment and deliver up to 72% savings compared to pay-as-you-go, which is substantial but still less than the up to 90% discount from Spot VMs. They are designed for steady-state, always-on production workloads, not for fault-tolerant batch jobs that can be interrupted, making them more expensive and less appropriate than Spot VMs.
- ✓
Azure Spot VMs
Why this is correct
Azure Spot VMs leverage unused Azure capacity at discounts of up to 90%, making them the cheapest compute option for workloads that can tolerate interruption and eviction. Because batch jobs are inherently fault-tolerant and can resume, Spot VMs are the ideal fit here; Azure may reclaim them with a 30-second notice, but that eviction risk is acceptable for this use case.
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Azure Dedicated Host
Why it's wrong here
Azure Dedicated Host provides a physical server dedicated to your workloads, which is useful for regulatory compliance or bringing your own licenses, but you pay for the entire host regardless of utilization. At premium pricing, it is the most expensive option, far exceeding the cost of Spot VMs, so it is not a cost-effective choice for a batch job.
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Azure Functions Consumption Plan
Why it's wrong here
The Azure Functions Consumption Plan is serverless and event-driven, scaling to zero when idle, and imposes a maximum execution duration (typically 5 minutes, up to 10 minutes) that is far too short for long-running batch jobs. It bills based on executions and resource consumption, not on dedicated compute time, making it inefficient and unsuitable for continuous batch processing.
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Senior Network & Security Engineer · founder of Courseiva
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