Reserved Instances and Savings Plans in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Reserved Instances Billing

You purchase a Standard Reserved Instance (RI) for an EC2 instance with a 3-year term and All Upfront payment. After 1 year, you stop using the instance but keep the RI. What happens to your billing?

A You stop paying for the instance immediately since you stopped using it.

B You pay only for the months you used the instance, and the rest is refunded.

C You continue paying the full upfront cost for the entire 3 years regardless of usage.

D You pay a monthly fee until you cancel the RI.

💡 Hint

Think about how upfront payments work for Reserved Instances.

Standard Reserved Instances with All Upfront payment require you to pay the full cost at purchase. You keep the reservation for the full term regardless of usage, so you continue to own the RI and its billing benefits even if you stop using the instance.

❓ service_behavior

intermediate

Savings Plans Flexibility

You have a Compute Savings Plan for $10/hour. You run different instance types across regions. Which statement is true about how your Savings Plan applies?

A The Savings Plan applies only to the exact instance type and region you specified.

B The Savings Plan applies to any EC2 instance usage regardless of region or instance family.

C The Savings Plan applies only to instances in the same Availability Zone.

D The Savings Plan applies only to instances with the same operating system.

💡 Hint

Consider the flexibility of Compute Savings Plans compared to Standard RIs.

Compute Savings Plans provide the most flexibility and apply to any EC2 instance usage regardless of region, instance family, or operating system, as long as the usage matches the committed spend.

❓ Architecture

advanced

Optimizing Cost with Reserved Instances and Savings Plans

Your company runs a mix of steady-state and variable EC2 workloads across multiple regions. You want to minimize costs while maintaining flexibility. Which combination is best?

A Use On-Demand instances only to maintain maximum flexibility.

B Purchase Standard Reserved Instances for all workloads in all regions.

C Use Scheduled Reserved Instances for all workloads to save costs during peak hours.

D Use Convertible Reserved Instances for steady workloads and Compute Savings Plans for variable workloads.

💡 Hint

Think about balancing cost savings and flexibility for different workload types.

Convertible RIs allow changing instance attributes for steady workloads, while Compute Savings Plans provide flexibility for variable workloads across regions and instance types, optimizing cost and flexibility.

❓ security

advanced

Security Implications of Reserved Instances Sharing

Your AWS account is part of an organization with consolidated billing. How does Reserved Instance sharing affect security and billing visibility?

A Reserved Instances are shared and billing benefits apply across accounts, but usage details are visible only to the payer account.

B Reserved Instances are shared across all accounts, but billing details remain private per account.

C Reserved Instances cannot be shared across accounts in an organization.

D Reserved Instances sharing exposes all account credentials to the payer account.

💡 Hint

Consider how consolidated billing works in AWS Organizations.

Reserved Instances purchased by the payer account apply across linked accounts for billing benefits. Usage details are visible to the payer account, but account credentials remain secure and private.

✅ Best Practice

expert

Choosing Between Standard and Convertible Reserved Instances

Your team expects to change instance types and operating systems frequently over the next 3 years but wants to save costs. Which Reserved Instance type should you choose and why?

A Convertible Reserved Instances, because they allow exchanging for different instance types and OS during the term.

B Standard Reserved Instances, because they can be sold on the Reserved Instance Marketplace if needs change.

C Standard Reserved Instances, because they offer the highest discount and allow instance type changes.

D No Reserved Instances, only On-Demand, to maintain full flexibility.

💡 Hint

Think about flexibility in changing instance attributes over time.

Convertible Reserved Instances allow exchanging the RI for different instance types, OS, or tenancy during the term, providing flexibility with cost savings. Standard RIs do not allow such exchanges.