OpenTelemetry Core Principles 1. Three pillars, one setup — Configure traces, metrics, and logs through a single call. Use for cross-cutting export to any OTLP-compatible backend. 2. Use for metrics — Never create instances with . The factory manages lifetime through DI and prevents leaks. 3. Null-safe activities — returns when no listener is attached. Always use when setting tags or events. 4. Environment variables over code — Use and so deployments control telemetry routing without code changes. 5. Low-cardinality metric tags — Keep metric tag combinations under 1000 per instrument. Use spa…