Most Cost-Effective Billing Model for Intermittent EC2 Workloads
Short answer
D Use On-Demand Instances to pay only for compute time used during the brief weekly and monthly reporting windows.
Question
Key Takeaways
Tests understanding of cost optimization for intermittent workloads where instances are shut down frequently, ruling out long-term commitments.
Determines the optimal AWS billing model for periodic, non-continuous EC2 usage by comparing On-Demand Instances against Reserved and Capacity Reservation options.
Common mistake: Candidates often choose Reserved Instances or Capacity Reservations, mistakenly believing they save money despite the low utilization frequency.
Expert Analysis
Why the Answer Is Correct
On-Demand Instances (D) are the most cost-effective option because the workload is highly intermittent (once a week and once a month). With On-Demand pricing, you pay only for the compute time used without any upfront commitment or long-term contract, which minimizes costs for sporadic usage.
Why the Other Options Are Wrong
Standard Reserved Instances (A) and Convertible Reserved Instances (B) require a 1-year or 3-year commitment for significant discounts, making them expensive for workloads that run less than 5% of the time. On-Demand Capacity Reservations (C) guarantee capacity in an Availability Zone but do not offer pricing discounts compared to standard On-Demand; they are intended for ensuring availability, not reducing costs.
Community Comment Notes
The community consensus strongly favors Option D. As Yomijohnson noted, "On-Demand Instances are ideal for intermittent workloads... allowing the company to pay only for the compute time they use." Yak_Yeti clarified that Capacity Reservations serve a different purpose regarding availability rather than cost savings for idle periods.
Exam Strategy
Always evaluate the utilization rate before choosing Reserved Instances. If usage is sporadic or unpredictable, On-Demand Instances are typically cheaper than committing to reservations.
Frequently Asked Questions
Why not use Spot Instances?
Do Capacity Reservations save money?
Community Votes
67% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 3 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 3
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Yomijohnson 👍 2In this scenario, the application only runs periodically—once every week and at the end of the month. Since the EC2 instances can be shut down when not in use, On-Demand Instances are the most cost-effective option. On-Demand Instances are ideal for intermittent workloads that do not require long-term or consistent usage commitments, allowing the company to pay only for the compute time they use.
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Yak_Yeti 👍 1 Answered CAWS On-Demand Capacity Reservations and On-Demand Instances serve different purposes: 1. On-Demand Capacity Reservations: -Purpose: Reserve compute capacity in a specific Availability Zone for any duration. -Flexibility: Can be created, modified, or canceled at any time. -Use Cases: Ideal for ensuring capacity for business-critical workloads, regulatory requirements, and disaster recovery. 2. On-Demand Instances: - Purpose: Provide compute capacity without any upfront commitment. - Flexibility: Pay for compute capacity by the hour or second, depending on the instance type. - Use Cases: Suitable for applications with unpredictable workloads or short-term requirements(1). (1) https://aws.amazon.com/compare/the-difference-between-on-demand-instances-and-reserved-instances/.
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ShaiTay 👍 2 Answered DD. On-Demand Instances
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