Google Cloud Professional Cloud Developer Practice Test

The most effective approach in this scenario involves leveraging Cloud Logging and Cloud Monitoring to enhance monitoring capabilities, which justifies the selection of this answer. By using Cloud Logging, you can capture detailed logs about application performance, allowing for more granular insights into how your cloud applications are functioning. This can identify specific issues or anomalies that may be causing slow responses.

Simultaneously, Cloud Monitoring provides the tools to visualize and analyze those logs, set up alerts, and create dashboards that can help track performance metrics over time. This combined strategy allows for not only real-time monitoring but also the historical context needed to identify trends or recurring problems. Thus, this approach builds a more responsive and informative monitoring environment that addresses the immediate performance issues your legacy system cannot handle effectively.

The other options, while potentially offering some form of solution, do not holistically address the need for improved monitoring responsiveness and agility. Simply replacing the monitoring platform with Cloud Monitoring might overlook the benefits of gradual integration. Installing a Cloud Monitoring agent on Compute Engine instances would enhance monitoring on those specific instances but may not tackle broader performance monitoring across all cloud components. Lastly, migrating some traffic back to the old platform for A/B testing could hinder overall application performance rather than improve the responsiveness of the monitoring system.