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CLF-029
Which of the following is the most appropriate option for lowering the cost of long-running EC2 workloads?
Choices
Explanation and answer
Read the explanation and correct answer (spoiler — try answering first)
Correct answer: C. Consider Savings Plans or Reserved Instances
Explanation
For long-running, stable workloads, Savings Plans or Reserved Instances can lower the cost compared with On-Demand pricing in many cases.
Per-choice explanations
A. Keep CloudWatch Logs forever
Incorrect. Keeping logs indefinitely increases cost.
B. Always use only On-Demand pricing
Incorrect. On-Demand is flexible but can be more expensive for long, fixed-term use.
C. Consider Savings Plans or Reserved Instances
Correct. For long-term use, consider discount options.
D. Fix all data on storage for high-frequency access
Incorrect. Choosing storage according to access frequency is important.
Practical Use
EC2 has four billing models: On-Demand, Savings Plans, Reserved Instances (RI), and Spot Instances. On-Demand bills usage per second or per hour with no commitment, Savings Plans and RI discount the hourly unit price in exchange for a one-year or three-year commitment, and Spot uses spare capacity at a heavy discount in exchange for the risk of interruption. For workloads that run stably over the long term, combining Savings Plans or RI can reduce cost by up to around 70 percent compared with On-Demand. Savings Plans commit to a hourly spend amount that applies across EC2, Fargate, and Lambda. Compute Savings Plans are particularly flexible because they automatically follow changes to the instance family, Region, OS, and tenancy. RI is EC2-specific. In exchange for specifying an instance type, Standard RI provides the highest discount rate and Convertible RI provides the flexibility to change the instance family. CLF-C02 only goes as far as asking whether to consider a discount option for long-term use, while SAA-C03 and above go deeper into the choice between Savings Plans and RI and the differences between Compute and EC2 Instance Savings Plans. Frequent distractors include "always use only On-Demand pricing," "keep CloudWatch Logs forever," and "fix all data on storage for high-frequency access," all of which increase cost rather than reduce it. The correspondence to remember is: long-term fixed usage equals a discounted commitment, highly variable usage equals On-Demand or serverless, and interruption-tolerant usage equals Spot.