Cost-Effective Scaling for Monolithic EC2 App

SAA-C03 By islever Editorial Last updated

Design secure workloads and applications. Design high-performing and elastic compute solutions.

Short answer

AE Use AWS Compute Optimizer to scale vertically for performance and create an Auto Scaling group with an ALB to scale horizontally for availability.

Question

A company hosts a monolithic web application on an Amazon EC2 instance. Application users have recently reported poor performance at specific times. Analysis of Amazon CloudWatch metrics shows that CPU utilization is 100% during the periods of poor performance. The company wants to resolve this performance issue and improve application availability. Which combination of steps will meet these requirements MOST cost-effectively? (Choose two.)
  1. Use AWS Compute Optimizer to obtain a recommendation for an instance type to scale vertically. Correct Answer
  2. Create an Amazon Machine Image (AMI) from the web server. Reference the AMI in a new launch template.
  3. Create an Auto Scaling group and an Application Load Balancer to scale vertically.
  4. Use AWS Compute Optimizer to obtain a recommendation for an instance type to scale horizontally.
  5. Create an Auto Scaling group and an Application Load Balancer to scale horizontally. Correct Answer

Key Takeaways

The exam tests the distinction between vertical scaling (performance fix) and horizontal scaling (availability), combined with the cost-effective use of AWS Compute Optimizer for sizing decisions.

This question addresses resolving CPU bottlenecks and improving availability for a monolithic application using AWS Compute Optimizer and Auto Scaling. It establishes that vertical scaling provides immediate performance relief while horizontal scaling ensures high availability.

Common mistake: Candidates often choose B and E, assuming an AMI is required for scaling. However, this ignores the immediate need to address the current CPU bottleneck via Compute Optimizer recommendations, making A and E the complete solution set.

Expert Analysis

Why the Answer Is Correct

The scenario requires two distinct outcomes: resolving poor performance (caused by 100% CPU) and improving availability. Option A uses AWS Compute Optimizer to recommend a larger instance type, which is the most cost-effective way to immediately resolve the CPU saturation on the existing monolithic architecture. Option E implements an Auto Scaling group with an Application Load Balancer to distribute traffic across multiple instances, directly addressing the availability requirement through horizontal redundancy.

Why the Other Options Are Wrong

Option B creates an AMI but does not implement any scaling or performance improvement mechanism on its own; it is merely a preparatory step. Option C suggests scaling vertically with Auto Scaling, which is technically incorrect as Auto Scaling inherently scales horizontally. Option D recommends horizontal scaling via Compute Optimizer, which is misleading because Compute Optimizer primarily helps size individual instances (vertical) rather than orchestrating horizontal scaling groups.

Community Comment Notes

Many learners debated between AE and BE, arguing that B is a prerequisite for E. As rpmaws noted, "AWS Compute Optimizer analyzes your current EC2 instance usage... so scaling vertically... could provide immediate relief." This highlights that without addressing the current overload (A), simply adding capacity later (E) doesn't solve the immediate performance crisis. Others like XXXXXlNN argued for BE based on long-term costs, but the prompt asks for the combination of steps to meet both requirements effectively now.

Official Reference

https://docs.aws.amazon.com/compute-optimizer/latest/ug/recommendations.html

This link opens the official vendor documentation in a new tab.

Exam Strategy

Always map each requirement in the question stem to a specific option. Here, 'poor performance' maps to Vertical Scaling (A) and 'improve availability' maps to Horizontal Scaling (E). Do not select preparatory steps (like creating an AMI) unless they are explicitly part of the active solution strategy requested.

Frequently Asked Questions

Why isn't creating an AMI (Option B) necessary?

An AMI is a static image. While useful for deployment, the question asks for steps to resolve performance and availability. Using Compute Optimizer (A) and Auto Scaling (E) are the active mechanisms that achieve these goals.

Can you scale vertically with Auto Scaling?

No. Auto Scaling groups manage the number of instances (horizontal scaling). Vertical scaling involves changing the instance type size, which is best guided by tools like AWS Compute Optimizer.

More SAA-C03 FAQ →

Community Votes

AE
52%
BE
48%

52% of anonymous learners picked answer AE. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 14 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 14

  1. rpmaws 👍 4
    AWS Compute Optimizer analyzes your current EC2 instance usage and recommends the most cost-effective instance type. In this case, the current instance may not have enough CPU capacity, so scaling vertically (upgrading to a larger instance type) could provide immediate relief from the 100% CPU utilization.
  2. Bwhizzy 👍 3
    The answer is A and E. A for adding more CPU (Vertical scaling ) and E for adding more Servers (Horizontal scaling)
  3. LeonSauveterre 👍 2
    What you should know: 1. Horizontal Scaling (Scaling Out/In): Adding or removing instances to distribute the load across multiple servers, improving availability and fault tolerance. Example: Using an Auto Scaling group with a load balancer to add more EC2 instances dynamically as demand increases. 2. Vertical Scaling (Scaling Up/Down): Increasing or decreasing the size (compute power, memory, etc) of a single instance, which is easier to implement for monolithic applications but has limitations (limited instance types). Example: Upgrading an instance from "t3.medium" to "m5.large". If you can understand above, then A & E are perfect choices. B - The performance issue is still there! C - Auto Scaling and Load Balancers are used for horizontal scaling, not vertical scaling. D - Horizontal scaling involves adding more instances, not changing the instance type.
  4. Anyio 👍 2
    The correct answers are A,E. Option A: Correct. Using AWS Compute Optimizer to obtain a recommendation for an instance type to scale vertically is an effective first step. This service analyzes your specific application workload patterns and recommends an appropriate EC2 instance type that provides better performance for the given CPU load. This approach allows you to choose a more powerful instance that can handle peak loads more effectively without immediately shifting to a horizontal scaling architecture. Option B: Incorrect by itself. Creating an AMI and a launch template is useful in setting up an Auto Scaling group or new instances but does not address the issue of CPU utilization or availability on its own. This process would be part of preparing for scaling but doesn’t directly answer the requirement of resolving performance issues by itself.
  5. XXXXXlNN 👍 2
    BE makes more sense to me. Vertical scaling increases cost continuously even when the instance is in low demand. for a long run, the cost would be higher than just scale horizontally. The questions says the 'poor performance at specific times', so we just need to scale up at specific times. Additionally, in order to scale up, we do need AMI and a launch template. Thus, a combination of B & E should be the correct answer
Show 9 more comments
  1. Salilgen 👍 2
    The question talk about a "combination of steps" then IMO answer is BE. BE are steps of a solution that resolve performance issue and improve application availability. D is for improve the solution : https://docs.aws.amazon.com/compute-optimizer/latest/ug/view-asg-recommendations.html A is a solution (not a step) but it is not the most cost effective C is wrong: autoscaling and ALB are horizontal scaling
  2. FlyingHawk 👍 2
    The question asks for a combination of steps, meaning the selected answers should work together to form a complete solution rather than being two independent actions. B - prepared the instance for the scaling E - Implement Auto Scaling for performance improvement and high availability
  3. Abdullah2004 👍 2
    Due to monolithic application we can't scale horizontal, the scale will be vertical
  4. JA2018 👍 1
    What about options D & E? # 1 Scaling horizontally is the most cost-effective solution for handling fluctuating traffic, especially when the bottleneck is CPU utilization reaching 100% during peak times. This allows adding more instances to handle the increased load instead of upgrading to a larger instance (vertical scaling) which might be unnecessary during non-peak periods. # 2 Auto Scaling group and Application Load Balancer: These are essential components for horizontal scaling, where the Auto Scaling group automatically adjusts the number of instances based on demand, and the Application Load Balancer distributes traffic evenly across available instances. #3 AWS Compute Optimizer: This service can analyze your application usage and recommend the most cost-effective instance type for your specific needs, including suggesting options for horizontal scaling.
  5. EllenLiu 👍 1
    it's truly difficult to answer as per the description. there are two requirement: 1. resolve performance issue => A: use compute optimizer to scale vertically, it can provides an immediate fix for high CPU utilization 2. improve availability => B + D, B is the prerequisite for D , I prefer autoscaling if must choose only one
  6. dfgdsfgfdgreg 👍 1
    Since options C and D are irrelevant, let's disregard them. That leaves us with ABE. B is a prerequisite for E, so you cannot have E with B. AB will be two disjointed choices. So you have to choose B/E.
  7. jfedotov 👍 1
    horizontal scaling is a cost-effective solution
  8. flaviobrf 👍 3
    BE is the right choice
  9. komorebi 👍 2
    Answer is BE

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