Firebase Performance Monitoring tracks app performance from the user's perspective. Traces between start and stop events. Screen traces automatically track Activity and Fragment rendering. HTTP request traces monitor network call performance. Custom traces measure specific code paths and operations. Attributes provide context like experiment group or content type. Metrics capture numeric values like cache hit count. Slow rendering traces identify UI jank and frame drops. Network request monitoring captures latency, payload size, and success rate. Rate limiting prevents excessive data collection. Performance thresholds trigger alerts for degrading performance. Trace filtering focuses on specific app versions or device types. Console dashboard shows performance over time. Device segmentation identifies performance by hardware type. Network conditions affect performance across different connection types. APK size impact through minimal SDK overhead. Performance Monitoring helps identify real-world bottlenecks before users report them. Cold start traces measure app launch time. Screen rendering traces identify layout performance issues. Data retention is configurable for compliance requirements.