An organization’s application needs to monitor application-specific events with a standard AWS service. The service should capture the number of logged-in users and trigger events accordingly. During peak times, monitoring frequency will occur every 10 seconds.
What should be done to meet these requirements?
 

Answer options:

A.Create an Amazon SNS notification.
B.Create a standard resolution custom Amazon CloudWatch log.
C.Create a high-resolution custom Amazon CloudWatch metric.
D.Create a custom Amazon CloudTrail log.

Answer – C
This is clearly mentioned in the AWS Documentation.
When creating an alarm, select a greater than or equal period to the frequency of the metric to be monitored. For example, basic monitoring for Amazon EC2 provides metrics for your instances every 5 minutes. When setting the alarm on a basic monitoring metric, select a period of at least 300 seconds (5 minutes). Detailed monitoring for Amazon EC2 provides metrics for your instances every 1 minute. When setting the alarm on a detailed monitoring metric, select a period of at least 60 seconds (1 minute).
If you set the alarm on a high-resolution metric, you can specify a high-resolution alarm with a period of 10 seconds or 30 seconds, or you can set a regular alarm with a period of any multiple of 60 seconds.
Option A is incorrect since the question does not mention anything on notifications.
Option B is incorrect since the standard resolution counters will not help define triggers within a 10 second interval.
Option D is incorrect since Cloudtrail is used for API Activity logging.
For more information on Cloudwatch metrics, please refer to the below Link-
https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/cloudwatch_concepts.html