Question 648 of 302
Reducing EC2 Costs with Purchase Options and Auto Scaling Strategies
A company is running a production web application on Amazon EC2 instances behind an Application Load Balancer (ALB). The workload has predictable traffic spikes during business hours and low traffic at night. The current architecture uses On-Demand EC2 instances, leading to high costs. The company wants to reduce costs without sacrificing availability or performance. Which three of the following strategies would help achieve this goal? (Choose three.)
Quick Answer
The stem describes a workload with a clearly predictable rhythm, spikes during business hours, low traffic at night, and that predictability is the key detail, because it means capacity needs can be anticipated on a schedule rather than reacted to after the fact. A scheduled scaling action that adds capacity before business hours begin and removes it afterward directly matches infrastructure to that known pattern, so the fleet isn't sized for peak traffic around the clock, which is where the waste in an always-On-Demand setup comes from. This complements a companion strategy worth understanding in the same scenario: purchasing Reserved Instances for the portion of capacity that runs steadily around the clock captures a substantial discount over On-Demand pricing for that baseline, while scheduled scaling handles the variable portion that comes and goes with business hours. Together they split the workload into its predictable steady-state component and its predictable time-of-day component, and apply the right pricing and provisioning model to each rather than treating all capacity as one undifferentiated block running On-Demand. Neither piece alone would fully capture the savings available, since Reserved Instances wouldn't shed the off-hours capacity and scheduled scaling wouldn't discount the baseline. When a scenario describes traffic with a known daily pattern alongside a cost-reduction goal, look for a combination of purchase-commitment savings on the steady baseline and scheduled scaling on the predictable variable portion.
⚠ Common exam trap
Watch out — candidates often think Spot Instances can be used for the entire workload during peak hours, but they overlook the interruption risk and the requirement for the workload to be fault-tolerant, which a production web application behind an ALB typically is not without careful design.
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
✓
Purchase Reserved Instances for the baseline capacity that runs 24/7.
Purchasing Reserved Instances for the baseline 24/7 capacity provides a significant discount (up to 72%) compared to On-Demand pricing, directly reducing costs for the always-running portion of the workload. This strategy is correct because it matches the predictable, steady-state traffic component without sacrificing availability or performance.
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Same concept, more angles
1 more way this is tested on SAA-C03
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company runs a web application on Amazon EC2 instances behind an Application Load Balancer. The workload is predictable during business hours but has low usage at night. Which three options can reduce costs without compromising performance? (Choose three.)
medium- ✓ .Configure a scheduled auto scaling policy to reduce the number of instances during off-peak hours.
- .Use a single large EC2 instance to handle all traffic, reducing the number of running instances.
- .Use EC2 Spot Instances for the entire workload to achieve the lowest possible cost.
- ✓ .Implement a scaling policy based on CPU utilization to right-size the fleet dynamically.
- ✓ .Purchase Compute Savings Plans to cover the baseline EC2 usage during business hours.
- .Replace the Application Load Balancer with a Network Load Balancer, which is cheaper per hour.
Why : To reduce costs without compromising performance for a web application with predictable peak and low usage: 1. **Scheduled Auto Scaling:** Configuring a scheduled Auto Scaling policy allows you to automatically reduce the number of EC2 instances during known off-peak hours (e.g., nights and weekends) and scale them back up for business hours. This directly reduces hourly instance costs when demand is low without impacting performance during peak times. 2. **Dynamic Scaling based on CPU Utilization:** Implementing a dynamic scaling policy (e.g., target tracking based on CPU utilization) ensures that the EC2 fleet automatically scales in when demand (and thus CPU usage) is low, and scales out when demand increases. This right-sizes the fleet to current needs, optimizing costs while maintaining performance. 3. **Compute Savings Plans:** Purchasing Compute Savings Plans provides significant discounts on EC2 usage (and other compute services) in exchange for a 1- or 3-year commitment to a consistent spend. This is ideal for covering the predictable baseline workload during business hours, reducing the effective hourly cost of those instances without affecting their performance or availability.
Last reviewed: Jun 11, 2026
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