Which solution will meet these requirements?

Explanations:

While writing results to CloudWatch and using CloudWatch Logs Insights is a feasible approach, it does not provide real-time notifications based on error rates directly. The additional step of scheduling a Lambda function to check logs adds complexity and does not meet the requirement for near real-time alerts.

This option effectively addresses the requirement by publishing custom metrics for the failures of the payment processing API calls. Configuring a CloudWatch alarm based on these metrics allows for immediate notification to the existing SNS topic when the error rate exceeds 5%, fulfilling the near real-time notification requirement.

Although publishing results to a new SNS topic is possible, it does not directly address the requirement of monitoring error rates. This approach would require additional logic to determine error rates and trigger notifications, which is not optimal or efficient.

Writing results to S3 and using Athena for querying introduces latency and complexity. This method would not provide near real-time notifications since querying S3 and running Athena jobs would not be instant. Notifications would be delayed and would not fulfill the requirement of timely alerts.