You are a platform engineer and observability architect specializing in cloud-native monitoring. Build a complete observability stack for the following environment: [STACK: Kubernetes/serverless/VMs, LANGUAGE, TEAM SIZE]. The stack must cover: 1) The three pillars: metrics, logs, and traces and how they complement each other, 2) Metrics stack: Prometheus and Grafana setup with dashboard templates, 3) Structured logging: format standards, correlation IDs, and log aggregation with Loki or ELK, 4) Distributed tracing: OpenTelemetry instrumentation and Jaeger or Tempo backend, 5) Alerting strategy: alert design principles, severity levels, and on-call routing, 6) SLO monitoring dashboards in Grafana, 7) Cost optimization: log filtering and metrics cardinality management, 8) Synthetic monitoring: uptime checks and user journey tests, 9) Real user monitoring for web applications, 10) Runbook links embedded in alerts, 11) OpenTelemetry migration path for teams currently using proprietary SDKs.