Aurora Multi-AZ Auto Scaling for Read-Heavy Ecommerce DB
A company runs an ecommerce application on Amazon EC2 instances behind an Application Load Balancer. The instances run in an Amazon EC2 Auto Scaling group across multiple Availability Zones. The Auto Scaling group scales based on CPU utilization metrics. The ecommerce application stores the transaction data in a MySQL 8.0 database that is hosted on a large EC2 instance. The database's performance degrades quickly as application load increases. The application handles more read requests than write transactions. The company wants a solution that will automatically scale the database to meet the demand of unpredictable read workloads while maintaining high availability. Which solution will meet these requirements?
Community Insight
The test measures whether you can match read-heavy, unpredictable demand plus high availability to Aurora Multi-AZ with Aurora Auto Scaling replicas; the trap is picking read scaling (RDS read replicas) or availability alone without both.
This SAA-C03 scenario asks how to replace a struggling self-managed MySQL EC2 database with a service that scales read capacity automatically and stays highly available. Aurora Multi-AZ (writer plus readable standby) combined with Aurora Auto Scaling of Aurora Replicas is the only option satisfying both the unpredictable read-scaling and high-availability requirements.
Option B is the most tempting wrong answer because it mentions reader instances in another Availability Zone, but it starts from a Single-AZ deployment, so the primary database has no synchronous standby and readers are added manually rather than scaled automatically for unpredictable load.
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Expert Analysis
Why the Answer Is Correct
Option C deploys Amazon Aurora in a Multi-AZ configuration, which places a synchronous standby in a second Availability Zone for fast failover, and adds Aurora Auto Scaling with Aurora Replicas so read capacity grows and shrinks with demand. Aurora is MySQL-8.0-compatible, so the existing application and transaction data migrate with minimal change, and Aurora delivers roughly a 5x throughput improvement over stock MySQL on the same hardware. Aurora Replicas share the same cluster volume as the writer instance, add no write overhead, and are targeted by the Multi-AZ reader endpoint for load balancing. Because the ASG scales on CPU, unpredictable read spikes are absorbed by adding replicas instead of vertical instance resizing, directly meeting the stated requirement.Official Reference
Exam Strategy
Read the requirement pairs: 'unpredictable read workloads' plus 'high availability' means you need both autoscaled read replicas and a Multi-AZ topology, and only Aurora (or RDS Multi-AZ with replicas) can offer both. On SAA-C03, treat 'automatically scale' as a signal for a managed autoscaling feature, not a manually added instance.
Frequently Asked Questions
Why is RDS with reader instances in another AZ (Option B) not correct?
Option B specifies a Single-AZ deployment, so the primary has no synchronous standby for high availability, and readers are added manually rather than autoscaled for unpredictable read demand.
Can Aurora Auto Scaling replicas replace the MySQL database on EC2 for an ecommerce app?
Yes. Aurora is MySQL-compatible, so schema and drivers carry over, and Aurora Replicas share the cluster volume to add read capacity without extra storage or write overhead.
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