DVA-C02 Exam Dumps : AWS Certified Developer - Associate

The correct answer is C because Amazon SNS subscription filter policies are the native AWS feature for ensuring that only messages with matching attributes are delivered to a specific subscription. In this scenario, the Lambda function should process only refund messages from an SNS topic that contains multiple payment activity message types. By applying a subscription filter policy to the Lambda subscription, SNS delivers only the refund-related notifications to the function.

This is the most operationally efficient solution because filtering happens before invocation of the Lambda function. That means the Lambda function is not triggered for irrelevant payment events, which reduces unnecessary invocations, lowers compute cost, and simplifies the function code. AWS documentation recommends using subscription filter policies with SNS when subscribers should receive only a subset of messages based on message attributes.

Option A is incorrect because Lambda event filtering is available for some event sources, but for SNS-to-Lambda integration , the AWS-native filtering point is the SNS subscription itself. Option B is less efficient because it still invokes the Lambda function for every message and then discards non-refund messages in code. That increases operational overhead and cost. Option D is unrelated to the requirement because batching changes invocation behavior but does not filter by message type.

Therefore, the best design is to publish all payment activity events to SNS with appropriate message attributes and configure an SNS subscription filter policy so that only refund messages invoke the Lambda function. This approach is simple, scalable, and aligns with AWS event-driven architecture best practices.

By default, an Auto Scaling group uses EC2 status checks to determine instance health. EC2 status checks confirm that an instance is running and reachable at the infrastructure level, but they do not validate that the application is healthy behind the load balancer. In this scenario, the ALB is returning HTTP 502 errors and the target group shows instances as unhealthy, meaning the application is failing health checks (or not responding correctly). However, because the Auto Scaling group is using the default EC2 health check type, it does not consider these instances unhealthy for replacement.

AWS recommends configuring the Auto Scaling group to use ELB health checks when instances serve traffic behind an ALB or NLB. With ELB health checks enabled, Auto Scaling evaluates target health as reported by the load balancer target group. If the ALB marks an instance unhealthy, the Auto Scaling group will treat that instance as unhealthy and terminate and replace it automatically, restoring capacity with healthy targets.

Why the other options are insufficient:

Cooldown period (A) affects scaling timing, not health replacement logic.

Lifecycle hook changes (B) can help with initialization timing, but they do not cause Auto Scaling to replace instances based on ALB target health unless ELB health checks are enabled.

Health check grace period (D) delays health evaluation after launch, which can reduce premature replacement, but it still won’t replace instances based on ALB target group status unless the health check type is ELB.

Therefore, switching the Auto Scaling group health check type to Elastic Load Balancing (ELB) is the correct fix.

Why Option D is Correct:When using a container-based AWS Lambda function, you are responsible for updating the base image for runtime patches. Rebuilding the container with the latest Node.js patch version ensures the function is updated with the required security patches. Publishing a new version of the Lambda function makes the updated image available for use.

Why Other Options are Incorrect:

Option A: The runtime update mode applies to functions using AWS-managed runtimes, not container-based runtimes.

Option B: Redeploying the same version of the Lambda function does not apply the security patch.

Option C: Rebuilding with the AWS OS base image does not guarantee that the latest Node.js patch version is included.

AWS Documentation References:

Lambda Function Container Images

Node.js Updates in AWS Lambda