Design Scalable and HA Web App with Aurora

SAA-C03 By islever Editorial Last updated

Design scalable and loosely coupled architectures. Design highly available and/or fault-tolerant architectures.

Short answer

BC Launch EC2 instances in an Auto Scaling Group across multiple AZs behind an ALB and migrate the database to an Aurora MySQL cluster with a reader in a separate AZ.

Question

A software company needs to upgrade a critical web application. The application currently runs on a single Amazon EC2 instance that the company hosts in a public subnet. The EC2 instance runs a MySQL database. The application's DNS records are published in an Amazon Route 53 zone. A solutions architect must reconfigure the application to be scalable and highly available. The solutions architect must also reduce MySQL read latency. Which combination of solutions will meet these requirements? (Choose two.)
  1. Launch a second EC2 instance in a second AWS Region. Use a Route 53 failover routing policy to redirect the traffic to the second EC2 instance.
  2. Create and configure an Auto Scaling group to launch private EC2 instances in multiple Availability Zones. Add the instances to a target group behind a new Application Load Balancer. Correct Answer
  3. Migrate the database to an Amazon Aurora MySQL cluster. Create the primary DB instance and reader DB instance in separate Availability Zones. Correct Answer
  4. Create and configure an Auto Scaling group to launch private EC2 instances in multiple AWS Regions. Add the instances to a target group behind a new Application Load Balancer.
  5. Migrate the database to an Amazon Aurora MySQL cluster with cross-Region read replicas.

Key Takeaways

The trap is confusing high availability within a region with cross-region disaster recovery; the correct solution focuses on multi-AZ scaling and intra-region read replicas.

This question tests designing a scalable, highly available architecture using Auto Scaling Groups, Application Load Balancers, and Amazon Aurora MySQL to reduce read latency.

Common mistake: Many learners select options involving cross-region configurations (like A or E) because they associate 'scalable' with global reach, missing that HA primarily requires redundancy within the active deployment region first.

Expert Analysis

Why the Answer Is Correct

To meet the requirements of scalability, high availability, and reduced read latency, Option B and Option C are the precise architectural choices. Option B creates an Auto Scaling group across multiple Availability Zones (AZs) behind an Application Load Balancer (ALB). This ensures that if one AZ fails, traffic routes to healthy instances in other AZs (HA), while the ASG adjusts capacity based on demand (scalability). Option C migrates the database to Amazon Aurora MySQL with a primary and reader instance in separate AZs. Aurora's replication provides high availability, and the reader instance offloads read traffic, directly addressing the requirement to reduce MySQL read latency.

Why the Other Options Are Wrong

Option A describes a Disaster Recovery (DR) setup using Route 53 failover across regions, which does not provide the low-latency scaling needed for a live web application and adds significant complexity. Option D is technically invalid because Auto Scaling Groups cannot span multiple AWS Regions; they are confined to a single region. Option E offers cross-Region read replicas, which improve DR and some latency scenarios but do not address the core application server scalability as effectively as Option B, and cross-region replication introduces higher latency than local AZ replicas for the primary use case described.

Community Comment Notes

The community consensus strongly favors BC. As Sarayounisaldossary noted, "Auto Scaling + Load Balancer across AZs... Gives: HA and Elastic scalability," correctly identifying the role of ALBs and ASGs. Another user emphasized that options like A and E are for "Disaster Recovery" rather than the immediate HA/scalability needs of the question. The vote distribution confirms this alignment with official exam doctrine.

Official Reference

These links open the official vendor documentation in a new tab.

Exam Strategy

Always distinguish between High Availability (multi-AZ) and Disaster Recovery (cross-region). When asked for scalability and HA, look for Auto Scaling Groups and Load Balancers within the same region, and for database performance, prioritize Read Replicas or Multi-AZ deployments over cross-region solutions.

Frequently Asked Questions

Why can't Auto Scaling groups span multiple regions?

AWS Auto Scaling Groups are region-specific resources. They manage capacity within a single AWS Region. To scale across regions, you must deploy separate ASGs in each target region.

Is cross-region read replica better for latency?

No. Cross-region read replicas introduce higher network latency compared to local AZ replicas. For reducing read latency in a primary region, local Aurora readers in different AZs are superior.

More SAA-C03 FAQ →

Community Votes

BC
100%

100% of anonymous learners picked answer BC. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 8 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 8

  1. example_ 👍 6
    https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/Concepts.AuroraHighAvailability.html
  2. JunsK1e 👍 4
    B is correct and C, D is incorrect since the auto scaling is working within Region not Multi region. E incorrect also because the question is asking a high availability C is the best answer that E.
  3. dhewa 👍 3
    These simple options will help you achieve a robust, scalable, and highly available architecture for your web application
  4. nebajp 👍 2
    correct Answer is B& C as it talks about high availability and scalability and rest of the options are for Disaster Recovery. Right answer is B & C.
  5. [Removed] 👍 2
    B and C for high availability and scalability
Show 3 more comments
  1. Sarayounisaldossary 👍 1
    B. Auto Scaling + Load Balancer across AZs Launch multiple EC2s across multiple AZs Add to Application Load Balancer Gives: HA and Elastic scalability C. Migrate to Aurora MySQL with a reader in a separate AZ Aurora is high performance + replication built-in Reader in another AZ → lower read latency Built for fault tolerance NOT A,D,E A. EC2 in another Region + Route 53 Failover: Disaster recovery, not real-time scaling or latency reduction. D. Auto Scaling across Regions: Not supported. E. Aurora with cross-Region replica: Overkill and not needed here.
  2. progounick 👍 2
    It is obvious
  3. komorebi 👍 1
    Answer is DE

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