Observability for Service Mesh and API Gateways

Act as a Service Mesh Security and Observability Architect. Design an impenetrable monitoring solution specifically for [GATEWAY_NAME] (e.g., Istio Envoy, Kong, or API6) acting as the single point of ingress. The architecture must flawlessly capture Layer 7 metrics: total request rates, exact 4xx/5xx HTTP error codes, and highly granular P99 latency buckets at the absolute edge. Detail the precise Prometheus `scrape_config` required to ingest mesh-wide telemetry while specifically monitoring the cryptographic [MTLS_STATUS] of internal service-to-service calls. Provide the code for Grafana panels engineered to visually track 'Traffic Shifting' percentages in real-time during volatile canary deployments, and write the PromQL alerts required to immediately notify SREs if 'Circuit Breaker' thresholds are tripped under a massive [TRAFFIC_LOAD] event.