Envoy vs Istio: What are the differences?

Envoy and Istio are popular technologies for managing and securing microservices in cloud-native environments. Envoy is a high-performance proxy, while Istio is a comprehensive service mesh platform. Here are the key differences between Envoy and Istio:

1. Scope and Functionality: Envoy is a high-performance, open-source edge, and service proxy designed for modern architectures. It focuses on handling network traffic between services, providing features like load balancing, routing, traffic management, and observability. Envoy acts as a data plane component and can be used independently or as part of other service mesh solutions. On the other hand, Istio is a full-featured service mesh platform that leverages Envoy as its default sidecar proxy. Istio provides a comprehensive set of capabilities for traffic management, security, policy enforcement, and observability. It acts as a control plane and manages the configuration and behavior of the Envoy proxies deployed alongside services.

2. Service Mesh Features: Istio provides additional features beyond what Envoy offers as a standalone proxy that includes intelligent routing, traffic splitting, canary deployments, fault injection, circuit breaking, service-level authentication, authorization, and observability through distributed tracing, metrics, and logging. These features allow developers to implement advanced traffic management and security patterns within their microservices architecture. Envoy, while powerful as a proxy, does not provide the same level of service mesh-specific features that Istio offers.

3. Architecture and Integration: Envoy is designed to be a standalone component that can be integrated into various application stacks. It supports different deployment scenarios and can be used with or without a service mesh. Envoy is language-agnostic and can be used with applications written in different programming languages. On the other hand, Istio is built on top of Envoy and provides a higher-level abstraction for managing service-to-service communication. Istio integrates deeply with Kubernetes and is often used in Kubernetes-based environments. Istio leverages Envoy's capabilities and provides a control plane for managing and configuring the Envoy proxies.

4. Complexity and Learning Curve: Envoy is a standalone proxy with a simpler learning curve, while Istio introduces additional complexity with its comprehensive feature set and control plane components. Envoy can be configured using its own files or APIs, while Istio requires working with custom resource definitions (CRDs) and specific components like gateways and virtual services.

In summary, Envoy and Istio are both powerful tools for managing and securing service-to-service communication in modern architectures. Envoy serves as a high-performance edge and service proxy, while Istio provides a complete service mesh platform built on top of Envoy.