These questions are independently created for study purposes. They are not official AWS exam questions, actual exam questions, leaked questions, or exam dumps.
SAA-025
You have a short-running batch job that can be retried if interrupted. To significantly reduce EC2 cost, which option is the most appropriate?
Choices
Explanation and answer
Read the explanation and correct answer (spoiler — try answering first)
Correct answer: D. Use Spot Instances
Explanation
Spot Instances suit workloads that can tolerate interruption and can significantly reduce cost compared with on-demand pricing.
Per-choice explanations
A. Add a NAT Gateway
Incorrect. Adding a NAT Gateway is not a way to reduce EC2 cost for batch processing.
B. Always use the largest on-demand instance
Incorrect. Always using the largest on-demand instance increases cost.
C. Use only Dedicated Hosts
Incorrect. Dedicated Hosts are used when licensing or other requirements call for a dedicated physical host. They are not a cost-reduction choice.
D. Use Spot Instances
Correct. They suit batch jobs that can be interrupted.
Practical Use
Spot Instances let you use spare EC2 capacity at up to 90% off on-demand pricing. In exchange, AWS can reclaim the capacity at any time, providing a Spot Instance interruption notice two minutes in advance before stopping the instance. This characteristic makes Spot suitable for retryable batch jobs, ML training, CI/CD builds, rendering, and data processing pipelines. Combining Spot with EC2 Auto Scaling groups and specifying multiple instance types via a mixed instances policy also avoids capacity shortages caused by exhaustion of a specific instance type. As a design rule of thumb, make Spot interruption handling idempotent and incorporate a checkpointing mechanism that saves intermediate state to S3 or DynamoDB so processing can resume. Receiving interruption notices via CloudWatch Events / EventBridge and executing graceful shutdown through an Auto Scaling Lifecycle Hook is also a common pattern. For workloads that need constant availability, combine On-Demand or RI / Savings Plans for the baseline and limit Spot to elastic capacity that scales up and down. On SAA-C03, conditions such as "short-running batch," "can be retried if interrupted," and "significantly reduce cost" point to Spot. Dedicated Hosts target requirements for dedicated physical hosts (such as bring-your-own license or physical isolation) and are not primarily a cost-reduction option. Always running the largest on-demand instance or adding a NAT Gateway either increases cost or is unrelated. Spot Fleet, mixed instances policies, and interruption-handling patterns are also asked in higher-level exams.