Azure Spot VMs for cost savings - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Azure Spot VM eviction behavior

You deploy an Azure Spot VM to save costs. What happens when Azure needs the capacity back?

A The VM is converted automatically to a standard pay-as-you-go VM.

B The VM is immediately deleted without warning.

C The VM continues running but with reduced performance.

D The VM is stopped and deallocated, allowing you to restart it later.

💡 Hint

Think about how Azure handles temporary resources and your ability to restart.

Azure Spot VMs are evicted by stopping and deallocating them, not deleting. This allows you to restart the VM later if capacity is available.

❓ Architecture

intermediate

Designing a fault-tolerant application using Azure Spot VMs

You want to use Azure Spot VMs for a batch processing job that can tolerate interruptions. Which architecture best supports this?

A Use a Virtual Machine Scale Set with Spot VMs and automatic reimaging on eviction.

B Deploy Spot VMs behind a load balancer with no autoscaling.

C Deploy a single Spot VM with no backup and manually restart if evicted.

D Use only standard VMs with reserved instances for guaranteed uptime.

💡 Hint

Consider how to handle VM evictions automatically and scale out.

Using a VM Scale Set with Spot VMs and automatic reimaging helps maintain capacity by replacing evicted VMs automatically, supporting fault tolerance.

❓ security

advanced

Security considerations for Azure Spot VMs

Which security risk is most relevant when using Azure Spot VMs for sensitive workloads?

A Spot VMs do not support encryption at rest.

B Spot VMs cannot be joined to Azure Active Directory.

C Spot VMs can be evicted unexpectedly, risking data loss if not properly backed up.

D Spot VMs expose public IPs by default, increasing attack surface.

💡 Hint

Think about what happens when a Spot VM is evicted suddenly.

Because Spot VMs can be evicted without notice, any data stored only on the VM's temporary disk can be lost. Proper backup and state management is essential.

❓ service_behavior

advanced

Spot VM pricing and eviction policy behavior

You set a maximum price for your Azure Spot VM. What happens if the current Spot price exceeds your max price?

A Your VM continues running until Azure evicts it for capacity reasons only.

B Your VM is immediately evicted because the price exceeded your max price.

C Azure automatically lowers your max price to keep the VM running.

D Your VM price is capped at your max price and continues running.

💡 Hint

Consider how Spot VM pricing controls eviction.

If the current Spot price rises above your max price, Azure evicts your VM immediately to avoid charging more than your set limit.

✅ Best Practice

expert

Optimizing cost and availability with Azure Spot VMs

You want to minimize costs using Azure Spot VMs but keep your application highly available. Which strategy is best?

A Combine Spot VMs with standard VMs across scale sets and configure automatic fallback to standard VMs on eviction.

B Use only Spot VMs with no fallback to standard VMs.

C Use Spot VMs and manually redeploy when evicted to save costs.

D Use standard VMs with reserved instances and avoid Spot VMs for availability.

💡 Hint

Think about balancing cost savings with uptime guarantees.

Combining Spot and standard VMs with automatic fallback ensures cost savings while maintaining availability during Spot VM evictions.

Practice

1. What is the main benefit of using Azure Spot VMs?

easy

A. They automatically scale without any configuration.

B. They offer significant cost savings by using unused capacity.

C. They provide unlimited storage for virtual machines.

D. They guarantee 100% uptime for critical applications.

Solution

1. Step 1: Understand Azure Spot VM purpose

   Azure Spot VMs use spare capacity in Azure data centers, which is cheaper but can be interrupted.

2. Step 2: Identify the main benefit

   The main benefit is cost savings by using this spare capacity, not guaranteed uptime or unlimited storage.

3. Final Answer:

   They offer significant cost savings by using unused capacity. -> Option B

4. Quick Check:

   Spot VMs = Cost savings [OK]

Hint: Spot VMs save money by using spare capacity [OK]

Common Mistakes:

• Thinking Spot VMs guarantee uptime
• Confusing Spot VMs with premium storage
• Assuming Spot VMs auto-scale without setup

2. Which Azure CLI command option is used to create a Spot VM?

easy

A. --priority Spot

B. --spot-enabled true

C. --priority Standard

D. --vm-type Spot

Solution

1. Step 1: Recall Azure CLI syntax for Spot VMs

   To create a Spot VM, the correct option is --priority Spot.

2. Step 2: Eliminate incorrect options

   --priority Standard is for regular VMs; --spot-enabled and --vm-type are not valid Azure CLI options.

3. Final Answer:

   --priority Spot -> Option A

4. Quick Check:

   Spot VM creation uses --priority Spot [OK]

Hint: Use --priority Spot to create Spot VMs [OK]

Common Mistakes:

• Using --priority Standard instead of Spot
• Assuming --spot-enabled is valid
• Confusing VM type options

3. What happens if the max price you set for an Azure Spot VM is lower than the current Spot price?

medium

A. The VM will run but be charged the max price you set.

B. The VM will be created but with reduced performance.

C. The VM creation will fail due to price limit.

D. The VM will be created as a standard VM instead.

Solution

1. Step 1: Understand max price behavior

   The max price sets the highest price you agree to pay for the Spot VM.

2. Step 2: Analyze what happens if max price is too low

   If the current Spot price is higher than your max price, Azure will not create the VM to avoid exceeding your limit.

3. Final Answer:

   The VM creation will fail due to price limit. -> Option C

4. Quick Check:

   Max price below Spot price = VM creation fails [OK]

Hint: Spot VM fails if max price is below current Spot price [OK]

Common Mistakes:

• Thinking VM runs at max price anyway
• Assuming VM downgrades performance
• Believing VM converts to standard automatically

4. You created a Spot VM but it was unexpectedly evicted. What is the most likely cause?

medium

A. The VM was manually deleted by another user.

B. The VM ran out of disk space.

C. The VM exceeded the max price you set.

D. Azure needed the capacity back for other workloads.

Solution

1. Step 1: Understand Spot VM eviction reasons

   Spot VMs can be evicted when Azure reclaims capacity for higher priority workloads.

2. Step 2: Identify the most common eviction cause

   The most common cause is Azure needing the capacity back, not disk space or manual deletion.

3. Final Answer:

   Azure needed the capacity back for other workloads. -> Option D

4. Quick Check:

   Spot VM eviction = Azure reclaims capacity [OK]

Hint: Spot VMs evict when Azure reclaims capacity [OK]

Common Mistakes:

• Assuming eviction is due to disk space
• Thinking eviction happens if max price exceeded
• Believing eviction is always manual

5. You want to run a batch job that can be interrupted but must save costs. Which setup best uses Azure Spot VMs?

hard

A. Create Spot VMs with a max price set to your budget and use automatic eviction handling.

B. Create standard VMs with premium SSDs for guaranteed uptime.

C. Create Spot VMs without setting max price to avoid failures.

D. Use Azure Functions instead of VMs for batch jobs.

Solution

1. Step 1: Match workload needs to Spot VM features

   Batch jobs that can be interrupted fit Spot VMs well because they save costs but may be evicted.

2. Step 2: Choose best configuration for cost and reliability

   Setting a max price controls cost, and handling eviction automatically ensures job completion despite interruptions.

3. Step 3: Eliminate other options

   Standard VMs cost more; no max price risks failures; Azure Functions are different service types.

4. Final Answer:

   Create Spot VMs with a max price set to your budget and use automatic eviction handling. -> Option A

5. Quick Check:

   Spot VMs + max price + eviction handling = cost-effective batch jobs [OK]

Hint: Set max price and handle eviction for cost-effective Spot VMs [OK]

Common Mistakes:

• Not setting max price and risking high costs
• Choosing standard VMs for interruptible jobs
• Confusing Azure Functions with Spot VMs