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SAA-C03 Exam Question Walkthrough: Designing for Fault Tolerance
Learn how to approach a key SAA-C03 exam question on fault tolerance in AWS architectures. Understand the correct answer and why others fail.
Many candidates struggle with questions about fault tolerance in AWS architectures. This specific decision often trips up test-takers because it involves understanding how to maintain application availability across multiple Availability Zones.
The question
A company has a legacy application running on-premises that it wants to migrate to AWS. The application requires a high level of fault tolerance and should remain operational even if an entire Availability Zone fails. What architecture should the company implement?
- A. Deploy the application across multiple EC2 instances in a single Availability Zone.
- B. Use Amazon RDS with Multi-AZ deployments.
- C. Set up the application across multiple Availability Zones with load balancing.
- D. Implement a backup solution using AWS Backup.
Think before you scroll
Before you choose an option, consider the requirements for high availability and fault tolerance. The question emphasizes the need for operational continuity even during the failure of an entire Availability Zone. Evaluate the options with this in mind.
The answer
The correct option is C: Set up the application across multiple Availability Zones with load balancing. This architecture allows the application to remain operational if one Availability Zone fails, as the load balancer can distribute traffic to instances in other zones.
Why the other options lose
- A. Deploy the application across multiple EC2 instances in a single Availability Zone. This option fails to provide fault tolerance. If the single Availability Zone experiences an outage, all instances will go down, leading to total application failure.
- B. Use Amazon RDS with Multi-AZ deployments. While this option adds resilience for database workloads, it does not address the fault tolerance of the entire application architecture. It focuses only on the database layer, which does not meet the requirement of keeping the application operational.
- D. Implement a backup solution using AWS Backup. A backup solution does not ensure fault tolerance during an outage. Backups are meant for recovery after failure, not for maintaining operational continuity during a failure event.
The concept behind it
The underlying principle here is the need for redundancy across multiple Availability Zones. In AWS, deploying applications in multiple zones with load balancing ensures that traffic is distributed and can remain available despite failures in any one zone. This architecture is crucial for applications requiring high availability.
Exam trap to remember
Always remember: Fault tolerance requires distribution. If your architecture relies on a single Availability Zone, it cannot be deemed fault-tolerant.