A company is running an ecommerce application on Amazon EC2. The application consists of a stateless web tier that requires a minimum of 10 instances, and a peak of 250 instances to support the application's usage. The application requires 50 instances 80% of the time.
Which solution should be used to minimize costs?

A. Purchase Reserved Instances to cover 250 instances.

B. Purchase Reserved Instances to cover 80 instances. Use Spot Instances to cover the remaining instances.

C. Purchase On-Demand Instances to cover 40 instances. Use Spot Instances to cover the remaining instances.

D. Purchase Reserved Instances to cover 50 instances. Use On-Demand and Spot Instances to cover the remaining instances.








 

Suggested Answer: D

Community Answer: D

Reserved Instances -
Having 50 EC2 RIs provide a discounted hourly rate and an optional capacity reservation for EC2 instances. AWS Billing automatically applies your RI's discounted rate when attributes of EC2 instance usage match attributes of an active RI.
If an Availability Zone is specified, EC2 reserves capacity matching the attributes of the RI. The capacity reservation of an RI is automatically utilized by running instances matching these attributes.
You can also choose to forego the capacity reservation and purchase an RI that is scoped to a region. RIs that are scoped to a region automatically apply the RI's discount to instance usage across AZs and instance sizes in a region, making it easier for you to take advantage of the RI's discounted rate.
On-Demand Instance -
On-Demand instances let you pay for compute capacity by the hour or second (minimum of 60 seconds) with no long-term commitments. This frees you from the costs and complexities of planning, purchasing, and maintaining hardware and transforms what are commonly large fixed costs into much smaller variable costs.
The pricing below includes the cost to run private and public AMIs on the specified operating system (ג€Windows Usageג€ prices apply to Windows Server 2003 R2,
2008, 2008 R2, 2012, 2012 R2, 2016, and 2019). Amazon also provides you with additional instances for Amazon EC2 running Microsoft Windows with SQL
Server, Amazon EC2 running SUSE Linux Enterprise Server, Amazon EC2 running Red Hat Enterprise Linux and Amazon EC2 running IBM that are priced differently.
Spot Instances -
A Spot Instance is an unused EC2 instance that is available for less than the On-Demand price. Because Spot Instances enable you to request unused EC2 instances at steep discounts, you can lower your Amazon EC2 costs significantly. The hourly price for a Spot Instance is called a Spot price. The Spot price of each instance type in each Availability Zone is set by Amazon EC2, and adjusted gradually based on the long-term supply of and demand for Spot Instances. Your
Spot Instance runs whenever capacity is available and the maximum price per hour for your request exceeds the Spot price.
Reference:
https://aws.amazon.com/ec2/pricing/reserved-instances/

https://aws.amazon.com/ec2/pricing/on-demand/

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-instances.html


This question is in SAA-C02 AWS Certified Solutions Architect – Associate Exam
For getting AWS Certified Solutions Architect – Associate Certificate




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