What metrics are included without consuming any DDUs?

The correct answer highlights that built-in OneAgent metrics are provided as part of the Dynatrace platform without consuming any Data Processing Units (DDUs). OneAgent is responsible for collecting a wide range of metrics and telemetry data directly from the monitored host or environment. These metrics are fundamental to the core functionality of Dynatrace and are included in the platform's capabilities by default, allowing for seamless monitoring and analysis of application performance, infrastructure health, and user experience.

When it comes to the other choices, while custom metrics from third-party applications or all KPIs from external databases could be valuable for monitoring, they typically require additional resources which may be quantified in terms of DDUs. Similarly, metrics from user-defined dashboards often involve the aggregation and visualization of data that can lead to the consumption of DDUs, since they depend on custom configurations and additional data processing overhead. Therefore, only built-in OneAgent metrics are guaranteed to be included without incurring any DDU costs, making them a fundamental and efficient choice for monitoring within the Dynatrace ecosystem.