Azure Savings Plans - Time & Space Complexity

Time Complexity: Azure Savings Plans

O(n * m)

Understanding Time Complexity

We want to understand how the time to calculate and apply Azure Savings Plans changes as the number of resources grows.

How does the system handle more resources when applying savings plans?

Scenario Under Consideration

Analyze the time complexity of the following operation sequence.

// Pseudocode for applying Azure Savings Plans
var resources = GetAllResources();
var savingsPlans = GetActiveSavingsPlans();

foreach (var resource in resources) {
  foreach (var plan in savingsPlans) {
    if (plan.AppliesTo(resource)) {
      ApplyDiscount(resource, plan);
      break;
    }
  }
}
    

This sequence checks each resource against active savings plans and applies the first matching discount.

Identify Repeating Operations

Identify the API calls, resource provisioning, data transfers that repeat.

• Primary operation: Checking each resource against each savings plan to find a match.
• How many times: For every resource, the system may check multiple savings plans until one applies.

How Execution Grows With Input

As the number of resources grows, the number of checks grows too, since each resource is compared to savings plans.

Input Size (n resources)	Approx. Api Calls/Operations
10	About 10 x number of savings plans
100	About 100 x number of savings plans
1000	About 1000 x number of savings plans

Pattern observation: The total operations grow roughly in direct proportion to the number of resources.

Final Time Complexity

Time Complexity: O(n * m)

This means the time to apply savings plans grows linearly with the number of resources and the number of savings plans.

Common Mistake

[X] Wrong: "Applying savings plans takes the same time no matter how many resources there are."

[OK] Correct: Each resource must be checked, so more resources mean more work and more time.

Interview Connect

Understanding how operations scale with resource count helps you design efficient cloud cost management solutions.

Self-Check

"What if we cached the matching savings plan for each resource type? How would the time complexity change?"

Practice

1. What is the main benefit of using Azure Savings Plans?

easy

A. Lowering costs by committing to use services over time

B. Increasing the speed of virtual machines

C. Automatically scaling app services

D. Improving security of cloud resources

Solution

1. Step 1: Understand the purpose of Azure Savings Plans

   Azure Savings Plans are designed to reduce costs by committing to use certain Azure services over a period.

2. Step 2: Compare options to the main benefit

   Options A, B, and D describe performance or security improvements, which are not the primary goal of Savings Plans.

3. Final Answer:

   Lowering costs by committing to use services over time -> Option A

4. Quick Check:

   Cost savings = Lowering costs by commitment [OK]

Hint: Savings Plans reduce cost by commitment, not performance [OK]

Common Mistakes:

• Confusing cost savings with performance improvements
• Thinking Savings Plans improve security
• Assuming Savings Plans scale resources automatically

2. Which of the following is the correct Azure CLI command to create a savings plan?

easy

A. az savingsplan deploy --name MyPlan --scope subscription

B. az savingsplan new --name MyPlan --scope subscription

C. az savings create --plan MyPlan --scope subscription

D. az savings-plan create --name MyPlan --scope subscription

Solution

1. Step 1: Identify the correct Azure CLI syntax for savings plans

   The official command to create a savings plan uses az savings-plan create with parameters like --name and --scope.

2. Step 2: Check other options for invalid commands

   Options B, C, and D use incorrect verbs or command structures not supported by Azure CLI.

3. Final Answer:

   az savings-plan create --name MyPlan --scope subscription -> Option D

4. Quick Check:

   Correct CLI command = az savings-plan create [OK]

Hint: Use 'az savings-plan create' to make a new plan [OK]

Common Mistakes:

• Using 'new' instead of 'create' in CLI
• Mixing 'savings' and 'savingsplan' commands
• Incorrect parameter names

3. Given a steady workload of virtual machines running 24/7, what is the expected behavior when applying an Azure Savings Plan?

medium

A. Costs for the virtual machines will decrease due to the commitment

B. Virtual machines will automatically increase CPU cores

C. The workload will be moved to a cheaper region

D. Virtual machines will restart daily to apply savings

Solution

1. Step 1: Understand how Savings Plans affect steady workloads

   Azure Savings Plans reduce costs by committing to usage, so steady workloads like 24/7 VMs benefit from lower prices.

2. Step 2: Eliminate options unrelated to cost savings

   Options A, B, and C describe changes to performance, location, or VM behavior, which Savings Plans do not cause.

3. Final Answer:

   Costs for the virtual machines will decrease due to the commitment -> Option A

4. Quick Check:

   Steady workload + Savings Plan = Lower cost [OK]

Hint: Savings Plans cut cost, not change VM specs or location [OK]

Common Mistakes:

• Thinking Savings Plans change VM performance
• Assuming workload moves to cheaper regions automatically
• Believing VMs restart to apply savings

4. You tried to create an Azure Savings Plan but received an error: "Invalid scope parameter." What is the most likely cause?

medium

A. The savings plan name is too long

B. The scope value is not a valid subscription or resource group ID

C. You did not specify the VM size

D. The Azure CLI version is outdated

Solution

1. Step 1: Analyze the error message about scope

   The error "Invalid scope parameter" indicates the scope argument is incorrect or malformed.

2. Step 2: Identify what scope should be

   Scope must be a valid subscription ID or resource group ID; an invalid or mistyped value causes this error.

3. Final Answer:

   The scope value is not a valid subscription or resource group ID -> Option B

4. Quick Check:

   Invalid scope = wrong subscription/resource ID [OK]

Hint: Check scope is valid subscription or resource group ID [OK]

Common Mistakes:

• Ignoring scope format and using wrong IDs
• Blaming name length for scope errors
• Not updating Azure CLI before retrying

5. A company has fluctuating app service usage but wants to save costs with Azure Savings Plans. Which strategy best fits their needs?

hard

A. Avoid savings plans and pay pay-as-you-go only

B. Commit to the highest possible usage to cover all peaks

C. Commit to a savings plan based on their average steady usage to maximize savings

D. Create multiple savings plans for each app service separately

Solution

1. Step 1: Understand Savings Plans suit steady predictable usage

   Savings Plans work best when usage is steady; fluctuating usage means committing to average steady usage is optimal.

2. Step 2: Evaluate options for cost efficiency

   Commit to the highest possible usage to cover all peaks wastes money by committing to peak usage; C misses savings; D complicates management without extra benefit.

3. Final Answer:

   Commit to a savings plan based on their average steady usage to maximize savings -> Option C

4. Quick Check:

   Average steady usage commitment = best savings [OK]

Hint: Commit to average steady usage, not peaks, for best savings [OK]

Common Mistakes:

• Committing to peak usage wastes money
• Avoiding savings plans due to usage fluctuation
• Creating many small savings plans unnecessarily