envoy

An envoy is a diplomatic representative sent by a government to another country or to an international organization. Envoys may carry messages, negotiate agreements, and report on political developments. In modern practice the term can denote a diplomat of varying rank, such as a special envoy or personal envoy, who may have limited plenipotentiary authority and is not necessarily an ambassador. The highest diplomatic rank is typically ambassador. The Vienna Convention on the Diplomatic Relations of 1961 governs diplomatic privileges and immunities for accredited diplomats, including envoys, and provides the general framework for diplomatic missions and their conduct.

In computing, Envoy is an open-source edge and service proxy originally developed by Lyft and now a project under the Cloud Native Computing Foundation. It acts as a communication bus and load balancer for microservices, often deployed as a sidecar alongside application containers or as an edge gateway. Envoy offers features such as advanced load balancing, health checks, TLS termination, and support for HTTP/2 and gRPC, along with observability through metrics, tracing, and logging. It uses a dynamic configuration model via the xDS API, enabling centralized control of routing, resilience, and policy. Envoy is widely used in service mesh architectures; Istio and other platforms commonly rely on Envoy as their data plane.

Beyond diplomacy and computing, the term envoy can also refer to a messenger entrusted with conveying messages or representing a group in negotiations.