SAA-C03 Design Resilient Architectures Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Configure the ECS service to use a spread placement strategy across Availability Zones.

  Why this is correct

  To achieve high availability and fault tolerance for a stateless web application, configuring the ECS service with a spread placement strategy across Availability Zones is essential. This ensures that tasks are distributed evenly across different physical locations within a region, preventing a single AZ failure from impacting the entire application. By spreading tasks, the application maintains resilience and continues operating even during localized outages.

• ✓

  Set a minimum healthy percent of 50 and a maximum percent of 200 in the ECS service deployment configuration.

  Why this is correct

  Setting a minimum healthy percent of 50 ensures that at least half of the desired number of tasks remain running and healthy during a service deployment, maintaining application availability. Concurrently, a maximum percent of 200 allows the ECS service to launch up to twice the desired task count, providing sufficient capacity for new tasks to start before old ones are terminated, facilitating smooth rolling updates without service interruption.

• ✗

  Place all ECS tasks in a single subnet to minimize network latency.

  Why it's wrong here

  Placing all ECS tasks within a single subnet severely compromises the application's fault tolerance and availability. While it might marginally reduce network latency between tasks, this configuration creates a single point of failure; an outage affecting that specific subnet or its Availability Zone would render the entire application inaccessible. Best practices for resilient cloud deployments mandate distributing resources across multiple subnets in distinct Availability Zones.

• ✓

  Use an Application Load Balancer (ALB) in front of the ECS service to distribute traffic across tasks.

  Why this is correct

  An Application Load Balancer (ALB) is the ideal choice for distributing incoming HTTP/HTTPS traffic across the ECS tasks of a web application. ALBs provide advanced routing capabilities, such as path-based or host-based routing, and perform health checks on tasks, automatically directing traffic only to healthy instances. This ensures efficient load distribution, enhances fault tolerance, and improves the overall availability of the stateless web application.

• ✗

  Store application session data in an attached EFS file system shared across all tasks.

  Why it's wrong here

  Storing application session data in an attached EFS file system contradicts the principle of a stateless web application, which should not maintain session state on the compute layer. Furthermore, EFS is a shared file system primarily designed for persistent storage, not optimized for high-performance session management. For stateful applications requiring session persistence, external, highly available services like Amazon ElastiCache or Amazon DynamoDB are more appropriate and performant.

• ✗

  Disable automatic task replacement to avoid unnecessary task churn during failures.

  Why it's wrong here

  Disabling automatic task replacement for an ECS service would severely undermine the application's resilience and availability. This critical feature ensures that unhealthy or failed tasks are automatically stopped and replaced with new, healthy ones, maintaining the desired task count and service capacity. Without automatic replacement, task failures would lead to a permanent reduction in application capacity and potential service outages, requiring manual intervention.

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