Envoy sidecar OOM kill causes connection drops and service outages

Envoy sidecar memory growth reaches Kubernetes memory limit, triggering OOM kill and pod restart. Causes dropped connections and brief outages for the affected service.

Check memory usage with kubectl top and pilot-agent stats. Review memory limits. Identify root cause (service mesh size, connection count, metrics cardinality, buffering, or access logs). Apply Sidecar resource to limit config scope, reduce metric cardinality, fix connection leaks, or increase memory limits appropriately.