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Difficulty: EasyAWS Pricing Models

A municipal government office is deploying two new workloads on Amazon EC2:

1. A community information database that must run continuously 24/7 for the next three years.
2. A citizen survey application that will run for exactly five days to collect feedback and must not experience any interruptions.

Which of the following EC2 pricing options should the office select to minimize costs for these workloads? (Select TWO.)

  1. Reserved Instances for the community information databaseAnswer
  2. On-Demand Instances for the citizen survey applicationAnswer
  3. C
    Spot Instances for the citizen survey application
  4. D
    Spot Instances for the community information database
  5. E
    Reserved Instances for the citizen survey application

Answer

To optimize costs and meet operational requirements, the municipal office should choose Reserved Instances for the three-year database workload and On-Demand Instances for the five-day survey application.
The community information database runs continuously for three years, making it ideal for the cost savings provided by Reserved Instances, which require a long-term commitment. The citizen survey application is a short-term workload that runs for only five days and must not be interrupted, making On-Demand Instances the most cost-effective and reliable choice because they require no commitment and guarantee instance availability.

Step-by-Step Solution

1
Evaluate the database workload requirements.
The database must run continuously 24/7 for three years, which represents a highly predictable, long-term steady-state workload.
Long-term predictable workloads are best optimized financially using commitment-based models such as Reserved Instances or Savings Plans.
2
Evaluate the citizen survey application requirements.
The application runs for exactly five days (short-term) and must not be interrupted.
Since the workload is short-term, a long-term commitment is wasteful. Because it cannot tolerate interruption, Spot Instances are ruled out, leaving On-Demand as the best fit.
3
Match the evaluations to the correct combination of options.
Reserved Instances are mapped to the database workload, and On-Demand Instances are mapped to the survey workload.
This combination ensures maximum discount for the long-running database while avoiding commitment waste and interruption risks for the short-term survey.

Key Concept

EC2 pricing models are designed for different workload characteristics: Reserved Instances offer discounts for long-term commitments, On-Demand provides flexibility and reliability for short-term workloads, and Spot offers steep discounts for flexible, interruptible workloads.
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AWS Pricing Models

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