SAA-C03 Design Cost-Optimized Architectures Practice Question

A company runs a web application on Amazon EC2 instances in multiple Availability Zones. The application uses an Application Load Balancer and an Auto Scaling group. The company wants to reduce cost while maintaining high availability. The workload is steady and predictable, and the instances run continuously. Which two actions will reduce cost? (Choose two.)

⚠ Common exam trap

The trap here is treating availability features or load balancer types as cost optimizations, when the real savings for steady workloads come from commitments and right-sizing.

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

✓

Right-size the instances based on CloudWatch metrics to eliminate over-provisioned capacity.

For a steady, continuously running workload, the two most effective cost levers are purchasing commitments and right-sizing. Compute Savings Plans reduce the effective rate for the baseline usage, and right-sizing removes capacity that is not needed. High-availability features and load balancer choices should be preserved unless they are proven to be the primary cost driver.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
Move the application to a single Availability Zone to reduce data transfer charges.
Why it's wrong here
Consolidating into one Availability Zone may reduce cross-AZ data transfer, but it eliminates the high-availability design and exposes the application to a zone failure. The cost saving is usually small compared with the risk. The requirement explicitly includes maintaining high availability, so this option violates the design goal.
✓
Right-size the instances based on CloudWatch metrics to eliminate over-provisioned capacity.
Why this is correct
Right-sizing analyzes utilization metrics such as CPU, memory, and network to identify instances that are larger than needed. Moving to a smaller instance type reduces the hourly rate while still meeting performance requirements. For a steady workload, this is a reliable way to cut cost without sacrificing availability, provided the new size is validated under load.
✗
Enable termination protection on all instances to prevent accidental deletion.
Why it's wrong here
Termination protection is a safety feature that prevents accidental termination of instances, but it has no effect on the hourly charges. It does not reduce cost and may even hinder legitimate scaling actions. For cost optimization, you need purchasing options or right-sizing, not protection settings.
✗
Replace the Application Load Balancer with a Network Load Balancer to reduce hourly charges.
Why it's wrong here
Network Load Balancers and Application Load Balancers have different pricing models and capabilities. Replacing an ALB with an NLB may not reduce cost and could break layer 7 routing features the application depends on. Load balancer charges are typically a small fraction of EC2 cost, so this does not address the main cost driver.
✓
Purchase Compute Savings Plans to cover the steady-state usage.
Why this is correct
Compute Savings Plans offer a discount in exchange for a commitment to a consistent amount of compute usage per hour for a one- or three-year term. Because this workload is steady and predictable, the commitment can be sized to match the baseline, reducing the effective hourly rate without changing the architecture. This is a direct cost reduction for continuous usage.

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SAA-C03 Design Cost-Optimized Architectures Practice Question

Why each option matters

Option-by-option breakdown

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