Cost-Effective Uninterrupted EC2 Purchasing Options
Short answer
A Standard Reserved Instances provide the deepest discount for steady-state, uninterrupted workloads compared to On-Demand or Convertible Reserved Instances.
Question
Which EC2 instance purchasing option will meet this requirement MOST cost-effectively?
Key Takeaways
This question tests the boundary between Spot Instances' cost savings and their interruption risk, requiring a steady-state pricing model instead.
For applications that must run continuously without interruption, Standard Reserved Instances are the most cost-effective EC2 purchasing option, offering up to a 72% discount over On-Demand pricing.
Common mistake: Choosing On-Demand Instances because no time commitment is specified, ignoring that On-Demand is the most expensive option for continuous workloads.
Expert Analysis
Spot Instance Interruption Risk Spot Instances offer the lowest computational cost but come with the explicit trade-off of potential interruption. When AWS reclaims the capacity, a Spot Instance is terminated with only two minutes of warning. The requirement to run "without interruption" strictly disqualifies Spot Instances (Option D), despite their cost advantage.
Steady-State Cost Optimization With Spot eliminated, the choice is between On-Demand (Option C) and Reserved Instances (Options A and B). On-Demand pricing is the highest baseline rate, designed for short-term, unpredictable, or testing workloads. For an application that runs continuously, On-Demand is the least cost-effective choice. Reserved Instances apply a billing discount to continuous On-Demand capacity in exchange for a 1-year or 3-year commitment. AWS exam doctrine treats a continuously running, uninterrupted application as a steady-state workload, which is the precise use case for Reserved Instances. The lack of a specified duration in the prompt is a common distractor; you are expected to infer that a persistent application justifies a commitment.
Standard vs. Convertible Discounts Between the two Reserved Instance types, Standard Reserved Instances (Option A) provide a significantly deeper discount—up to 72% off On-Demand pricing—compared to Convertible Reserved Instances (Option B), which offer up to 66% but allow changes to instance attributes. Because the question asks for the MOST cost-effective option and does not mention a need for flexibility, Standard Reserved Instances is the correct choice.
Official Reference
- https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-reserved-instances.html
- https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-spot-instances.html
These links open the official vendor documentation in a new tab.
Exam Strategy
When a question asks for the "most cost-effective" EC2 option but includes a "no interruption" constraint, immediately eliminate Spot Instances. Then, compare the remaining options for cost: On-Demand is the most expensive, while Reserved Instances offer significant discounts for continuous usage. Assume "continuous" implies a steady-state workload suitable for commitments unless the prompt specifies a very short duration.
Community Votes
60% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 6 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 6
-
robje 👍 6 Answered CThere is no time specified, so you cannot assume that the application will have to run for a year, which makes an on-demand more logical. • On-demand: Like a resort where you come and pay full price whenever you like. • Reserved: You plan ahead and commit to staying for one to three years, receiving a discount. • Savings plan: You commit to spending a specific amount monthly, allowing flexibility in room types. • Spot instances: Last-minute discounts for empty rooms, but you can be asked to leave if someone pays more. • Dedicated host: You book the entire resort building, having your own hardware. Capacity reservation: You book a room without certainty of staying, paying full price regardless.
-
AWSCGTest 👍 2 Answered AThe key requirements are: No interruption to the application Most cost‑effective option Standard Reserved Instances provide the highest discount (up to ~72%) compared to On-Demand pricing while guaranteeing capacity for 1- or 3-year commitments. They are ideal for steady-state applications that must run continuously.
-
pgchand 👍 2 Answered CReserved instances are Ideal for predictable, long-term, stable workloads. hear there is no duration hence On demnd is best option
-
d00b229 👍 2A. Standard Reserved Instances
-
Ramdac 👍 1 Answered AStandard Reserved Instances (RIs) are the most cost-effective option for applications that need to run continuously with predictable resource requirements. - A. Standard Reserved Instances — Correct. Offer discounts of up to 72% compared to On-Demand pricing with a 1-year or 3-year commitment. - B. Convertible Reserved Instances — Incorrect. Provide greater flexibility to change instance attributes, but generally offer smaller discounts than Standard RIs. - C. On-Demand Instances — Incorrect. Support uninterrupted workloads without a long-term commitment, but are more expensive for continuous usage. - D. Spot Instances — Incorrect. Offer discounts of up to 90%, but AWS can interrupt them with a two-minute warning.
Show 1 more comment
-
alia107 👍 1 Answered AStandard Reserved Instances
Reader comments & corrections
No reader corrections yet — spotted an error or have a note? Share it below.
Related Analysis
Practice All CLF-C02 Questions
Access 120 questions with complete answers and detailed explanations.
View Full CLF-C02 Practice Test →