What is a service mesh and what problems does it solve?

Service mesh is infrastructure layer handling service-to-service communication in microservices. Components: data plane (sidecar proxies like Envoy) and control plane (configuration management). Features: traffic management (routing, load balancing), security (mTLS, authentication), observability (tracing, metrics). Examples: Istio, Linkerd, Consul Connect. Solves: consistent networking policies, removing network code from apps, visibility into communication. Trade-offs: added complexity, latency, resource overhead.