Comprehensive and Detailed 250 to 300 words of Explanation (AWS documentation-based, no links):

The requirement is an automated notification 30 days before an imported ACM certificate expires, delivered to the security team via an existing SNS topic with email subscription. The most operationally efficient approach is to use Amazon EventBridge with the managed event type for ACM certificate expiration. ACM publishes an event when a certificate is approaching expiration, and EventBridge can match that event and route it directly to a target service without custom polling logic.

Option D uses an EventBridge rule for the ACM Certificate Approaching Expiration event and sets the SNS topic as the target. This directly delivers an alert to the existing notification channel (email via SNS) and requires minimal code and minimal ongoing maintenance. It also avoids building and scheduling a scanner that must enumerate certificates, calculate dates, handle pagination, and manage failures.

Option C sends the event to SQS. While SQS is useful for decoupling and buffering, the requirement is to notify the security team, and SNS is already configured for email delivery. Using SQS would add an extra consumer component to read from the queue and publish notifications, which is additional operational overhead.

Options A and B require a custom Lambda-based scanning solution. That introduces scheduling (for example, EventBridge schedule), logic to detect “30 days remaining,” error handling, and ongoing maintenance. Since ACM already emits a purpose-built event for expiring certificates, polling is unnecessary and less efficient.

Therefore, D is the best solution: it uses a native event from ACM, routes it through EventBridge, and notifies the security team through the existing SNS topic with the least operational effort.