envoyproxy/envoy

Envoy is a high-performance network proxy designed for cloud-native applications, specifically for microservices architectures where many small services need to communicate reliably with each other. A proxy is software that sits between two systems and manages the traffic passing between them, handling things like routing, load balancing (distributing requests across multiple servers), retries, timeouts, and observability (collecting metrics and logs about what is happening). Envoy can operate in different roles: as an edge proxy (sitting at the boundary of your network handling external traffic), as a sidecar proxy (running alongside each individual service in your system), or in the middle of your network as a service mesh component. The "service mesh" pattern places a proxy next to every service so that all network communication goes through a controlled, observable layer without requiring each service to implement its own networking logic. It is written in C++ for performance and is hosted by the Cloud Native Computing Foundation (CNCF), the same organization that manages Kubernetes and other widely adopted infrastructure tools. It implements a standard called the universal data plane API, which means it can be dynamically configured and managed by a control plane without restarting. You would use Envoy if you are building or operating a large distributed system, one made of many small services, and you need a reliable, observable, and configurable layer to handle the network traffic between them. It is commonly used as a foundational component in service mesh implementations.