AZ-900 Describe Azure architecture and services Practice Question
A company needs to run a large-scale batch processing job that runs daily for several hours. The job can tolerate interruptions if compute capacity is reclaimed. They want to minimize compute costs. Which Azure compute service is most cost-effective for this scenario?
⚠ Common exam trap
It's easy for candidates to choose Azure Functions thinking it is always the cheapest serverless option, but they overlook its execution time limits and unsuitability for long-running batch jobs, while Azure Batch with low-priority VMs is specifically designed for cost-effective, interruptible batch processing.
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 Batch with low-priority VMs
Azure Batch with low-priority VMs is the most cost-effective option because it allows you to run large-scale batch jobs using surplus Azure capacity at a significantly reduced cost (up to 80% less than dedicated VMs). The job can tolerate interruptions, and low-priority VMs can be preempted when Azure needs the capacity back, making this a perfect fit for the scenario.
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 Virtual Machines
Why it's wrong here
Deploying a large-scale daily batch job on Azure Virtual Machines requires you to manually provision, configure, and scale VMs, and you pay the full pay-as-you-go rate even when those machines are idle or waiting for tasks. There is no built-in job scheduler or automatic scaling based on queue depth, so you must build or install that orchestration yourself. For a job that is interruption-tolerant and cost-sensitive, this approach significantly increases both cost and administrative overhead.
When this WOULD be correct
A company needs to run a legacy application that requires full control over the operating system and must run continuously without interruptions. They need to install custom software and manage dependencies, and cost is less of a concern than flexibility.
- ✓
Azure Batch with low-priority VMs
Why this is correct
Azure Batch is a managed service built specifically for parallel and large-scale batch computing. By using low-priority (Spot) VMs, you leverage Azure's surplus compute capacity at a substantial discount compared to pay-as-you-go pricing, while Azure Batch automatically schedules tasks, handles retries, and scales the pool based on the job's queue. Since your workload is daily, interruptible, and large, low-priority VMs are the most cost-effective and operationally appropriate choice.
- ✗
Azure Functions
Why it's wrong here
Azure Functions is an event-driven, serverless compute service with execution timeout limits measured in minutes, not hours, and it is designed for short-running, request-based workloads. It does not natively support managing a pool of worker nodes or checkpointing a massive parallel batch across many hours. Because your daily batch job is long-running and requires a coordinated compute pool, Functions' execution time limits and event model make it inappropriate.
When this WOULD be correct
A company needs to run a small, event-driven job that processes a file upload and runs for under 10 minutes, with no tolerance for interruptions. They want to pay only for execution time and minimize costs.
- ✗
Azure Container Instances
Why it's wrong here
Azure Container Instances is a straightforward way to run individual containers, but it is not an orchestration or scheduling platform: you must manually launch and manage each instance, and pricing is based on per-second compute and memory allocation with no built-in discounted spot capacity for batch workloads. While you can use scripts to launch containers, you still need external logic to queue tasks, handle retries, and scale out. For a large, daily batch job needing substantial compute at low cost, the lack of automatic job scheduling and cluster-level management makes ACI inefficient and expensive at scale.
When this WOULD be correct
A company needs to run a containerized application that starts quickly, runs for a few minutes, and then stops, without managing underlying infrastructure. For example, a CI/CD pipeline task or a one-time data processing script.
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 Batch with low-priority VMsCorrect answer▾
Why this is correct
Azure Batch is a managed service built specifically for parallel and large-scale batch computing. By using low-priority (Spot) VMs, you leverage Azure's surplus compute capacity at a substantial discount compared to pay-as-you-go pricing, while Azure Batch automatically schedules tasks, handles retries, and scales the pool based on the job's queue. Since your workload is daily, interruptible, and large, low-priority VMs are the most cost-effective and operationally appropriate choice.
✗Azure Virtual MachinesWrong answer — click to see why▾
Why this is wrong here
Azure Virtual Machines do not offer the low-priority or preemptible pricing that allows significant cost savings for interruptible batch workloads. They are billed per hour regardless of usage, making them more expensive for large-scale daily batch jobs that can tolerate interruptions.
★ When this WOULD be the correct answer
A company needs to run a legacy application that requires full control over the operating system and must run continuously without interruptions. They need to install custom software and manage dependencies, and cost is less of a concern than flexibility.
Why candidates choose this
Candidates may think VMs are the most flexible and familiar option for any compute workload, overlooking the cost benefits of low-priority VMs in Azure Batch for interruptible jobs.
✗Azure FunctionsWrong answer — click to see why▾
Why this is wrong here
Azure Functions is event-driven and designed for short-lived, stateless workloads, not for large-scale batch processing that runs for several hours daily. It has a maximum execution timeout (default 5 minutes, up to 10 minutes for premium plan) and cannot tolerate interruptions by reclaiming compute capacity.
★ When this WOULD be the correct answer
A company needs to run a small, event-driven job that processes a file upload and runs for under 10 minutes, with no tolerance for interruptions. They want to pay only for execution time and minimize costs.
Why candidates choose this
Candidates may think Azure Functions is cost-effective because it offers a consumption plan with pay-per-execution pricing, but they overlook its execution time limits and unsuitability for long-running batch jobs.
✗Azure Container InstancesWrong answer — click to see why▾
Why this is wrong here
Azure Container Instances are designed for short-lived, bursty workloads, not long-running batch jobs. They lack the preemption capability of low-priority VMs, so they cannot tolerate interruptions to minimize costs.
★ When this WOULD be the correct answer
A company needs to run a containerized application that starts quickly, runs for a few minutes, and then stops, without managing underlying infrastructure. For example, a CI/CD pipeline task or a one-time data processing script.
Why candidates choose this
Candidates may think containers are always cheaper than VMs, but they overlook that ACI does not offer preemptible pricing, making it less cost-effective for long-running, interruption-tolerant batch jobs.
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.