What should the developer do to meet this requirement?

Explanations:

Configuring a high-resolution CloudWatch alarm allows the developer to receive notifications within 30 seconds of an issue occurring, as it can evaluate the custom metric at 1-second granularity. This enables timely alerts through Amazon SNS based on specific thresholds.

Setting up a custom CloudWatch dashboard does not directly lead to notifications; it is primarily for visualization and monitoring metrics. While it provides insights, it does not fulfill the requirement for timely alerts.

Amazon CloudWatch Logs Insights is used for querying and analyzing log data. It does not trigger alerts or notifications, so it does not meet the requirement of notifying the developer about application issues.

Changing to a default CloudWatch metric would not provide the necessary granularity (1 second) for timely alerts. Default metrics may have longer evaluation periods, which would delay notifications and not meet the requirement.