CLF-C02 Billing, Pricing, and Support Practice Question
A company runs non-critical batch analytics jobs that can be paused and restarted if interrupted. The jobs are flexible regarding when they run. Which EC2 purchasing option offers the lowest possible cost for this workload?
⚠ Common exam trap
It's easy for candidates to choose Reserved Instances thinking they always provide the best discount, but they fail to recognize that Spot Instances can be even cheaper for fault-tolerant, flexible workloads that can handle interruptions.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Spot Instances
Spot Instances offer the lowest possible cost because they use spare AWS EC2 capacity at a steep discount (up to 90% off On-Demand). Since the batch analytics jobs are non-critical, can be paused and restarted, and are flexible regarding when they run, they are an ideal fit for Spot Instances, which can be interrupted with a 2-minute warning when capacity is reclaimed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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On-Demand Instances
Why it's wrong here
On-Demand Instances bill at the full list price per second with no upfront or long-term commitment, which means you pay maximum unit cost for every vCPU-hour and GB-hour consumed. Since these batch jobs are explicitly interruptible and can tolerate shutdowns, running them on On-Demand ignores the opportunity to use surplus capacity at a fraction of the price. On-Demand is appropriate for unpredictable, non-interruptible workloads, not for cost-sensitive flexible batch processing.
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Reserved Instances
Why it's wrong here
Reserved Instances require a one- or three-year commitment in exchange for a lower hourly rate, making them economical only for steady, always-on workloads with predictable capacity needs. These batch jobs run occasionally and can be interrupted, so paying upfront or committing to a multi-year term locks you into paying for idle capacity when no batch is running. Using Reserved Instances here would eliminate the flexibility that Spot provides and would not result in the lowest possible compute cost.
- ✓
Spot Instances
Why this is correct
Spot Instances let you bid on unused EC2 capacity that AWS would otherwise leave idle, commonly delivering 60–90% lower hourly costs than On-Demand. AWS can reclaim the instance with a two-minute warning, but because the batch jobs can pause and restart where they left off, this interruption risk is acceptable. By designing the workload with checkpointing and an Auto Scaling group that replenishes interrupted instances, Spot becomes the lowest-cost compute option for this scenario.
- ✗
Dedicated Instances
Why it's wrong here
Dedicated Instances run on physical servers that are dedicated solely to your account, which isolates your hardware for compliance or licensing requirements but adds a premium to On-Demand pricing. They provide no discount for flexibility or interruption tolerance, and you still pay for the entire hour even if the batch job is stopped. Choosing Dedicated Instances would make the batch workload more expensive than both On-Demand and Spot, so it does not meet the cost-minimization goal.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CLF-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CLF-C02 exam.