Achieving High Availability with Auto Scaling and DynamoDB

SAA-C03 By islever Editorial Last updated

Design highly available and/or fault-tolerant architectures. Design cost-optimized compute solutions.

Short answer

D Modify the Auto Scaling group to use EC2 instances across three Availability Zones and migrate the embedded NoSQL database to Amazon DynamoDB by using AWS Database Migration Service (AWS DMS).

Question

A company has a web application that includes an embedded NoSQL database. The application runs on Amazon EC2 instances behind an Application Load Balancer (ALB). The instances run in an Amazon EC2 Auto Scaling group in a single Availability Zone. A recent increase in traffic requires the application to be highly available and for the database to be eventually consistent. Which solution will meet these requirements with the LEAST operational overhead?
  1. Replace the ALB with a Network Load Balancer. Maintain the embedded NoSQL database with its replication service on the EC2 instances.
  2. Replace the ALB with a Network Load Balancer. Migrate the embedded NoSQL database to Amazon DynamoDB by using AWS Database Migration Service (AWS DMS).
  3. Modify the Auto Scaling group to use EC2 instances across three Availability Zones. Maintain the embedded NoSQL database with its replication service on the EC2 instances.
  4. Modify the Auto Scaling group to use EC2 instances across three Availability Zones. Migrate the embedded NoSQL database to Amazon DynamoDB by using AWS Database Migration Service (AWS DMS). Correct Answer

Key Takeaways

It tests the understanding that true high availability requires multi-AZ distribution, while managed NoSQL services eliminate the heavy operational burden of maintaining database replication on EC2.

This question addresses designing highly available architectures by distributing EC2 instances across multiple Availability Zones and migrating embedded databases to managed services like DynamoDB for reduced operational overhead.

Common mistake: Learners often choose options that only address scaling (like adding AZs) but ignore the database bottleneck, or they mistakenly believe Network Load Balancers are better for web apps without considering the operational cost of the underlying database.

Expert Analysis

Why the Answer Is Correct

Option D is the correct answer because it addresses both the high availability requirement for the application and the eventual consistency/operational overhead requirements for the database. Modifying the Auto Scaling group to span three Availability Zones ensures the web tier remains available if one zone fails. Migrating the embedded NoSQL database to Amazon DynamoDB leverages a fully managed service that automatically handles replication, failover, and scalability, significantly reducing operational overhead compared to managing replication on EC2 instances.

Why the Other Options Are Wrong

Options A and B suggest replacing the ALB with a Network Load Balancer (NLB). While NLBs are powerful, ALBs are generally preferred for modern web applications due to their rich features like path-based routing and host-based routing; more importantly, these options fail to address the database's operational overhead or the single-AZ limitation properly in conjunction with the DB change. Option C improves application HA by adding AZs but retains the embedded database on EC2 instances. Maintaining custom replication logic for an embedded database across AZs introduces significant operational complexity and overhead, violating the "LEAST operational overhead" constraint.

Community Comment Notes

The community consensus strongly supports Option D, recognizing the dual benefit of multi-AZ deployment and managed database services. Users noted that while migrating data requires initial effort, the long-term reduction in administrative tasks makes DynamoDB superior. Some comments highlighted that keeping the embedded database is "frustratingly complex" operationally. One user questioned the use of AWS DMS for embedded databases, but in the context of exam scenarios, DMS is the standard tool cited for such migrations when moving from self-managed or embedded structures to managed cloud databases.

Exam Strategy

When asked for "least operational overhead," always prioritize managed services over self-managed solutions on EC2. Additionally, ensure you address all constraints: if "highly available" is required for the app, check if the solution distributes load across multiple Availability Zones.

Frequently Asked Questions

Why not keep the embedded database and just add AZs?

Maintaining custom replication and failover for an embedded database across AZs creates high operational overhead, violating the 'least overhead' constraint.

Is AWS DMS suitable for migrating embedded databases?

Yes, in the context of this exam scenario, AWS DMS is the recommended tool for migrating data from self-managed or embedded database engines to managed services like DynamoDB.

More SAA-C03 FAQ →

Community Votes

D
100%

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

Discussion 10 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 10

  1. Kezuko 👍 4 Answered D
    ASG for application HA + DynamoDB Scale for HA
  2. Andy_09 👍 4
    The correct option should be D
  3. LeonSauveterre 👍 2 Answered D
    Application Load Balancer (ALB) is better suited for HTTP/HTTPS traffic. A & B are out. Maintaining replication and failover for the embedded database across AZs is frustratingly complex and operationally intensive. Migration to DynamoDB requires initial effort but reduces long-term operational overhead. So D.
  4. Cali182 👍 2 Answered D
    Dynamo DB presents more advantages, because it would need less administrative effort
  5. 1Alpha1 👍 2 Answered D
    DynamoDB + Modifying the Auto Scaling group
Show 5 more comments
  1. NayeraB 👍 1
    But wouldn't migrating an embedded database to a new one introduce operational overhead now and in the future?
  2. freedafeng 👍 1
    I honestly don't think you can use db Migration service to migrate an embedding db.
  3. rubiteb 👍 1
    B as it's highly available and has less operational overhead than D.
  4. TruthWS 👍 1
    Option D: let focus on HA + Scaling
  5. HTHK 👍 1
    DDDDDDDDDDDDDDDDDD

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