Hystrix vs Istio: What are the differences?

### Introduction

Key differences between Hystrix and Istio:

1. **Service Resilience**:
Hystrix focuses on improving the resilience of individual services by providing circuit breakers, fallback mechanisms, and latency tolerance, while Istio emphasizes service resilience through its service mesh architecture, which enables load balancing, traffic shifting, and fault injection at the network level.

2. **Service Mesh vs Library**:
Hystrix is a library for adding fault-tolerance and latency tolerance to individual services, while Istio is a service mesh platform that manages communication between services across a distributed network, providing capabilities like traffic management, security, and monitoring.

3. **Platform Support**:
Hystrix is specifically designed for Java applications and integrates well with Spring Cloud and other Java frameworks, while Istio is a platform-agnostic solution that can be used with applications developed using various languages and frameworks, making it more versatile in a multi-language environment.

4. **Control Plane Functions**:
Istio includes a control plane that provides features like traffic management, policy enforcement, and telemetry collection to manage service communication, whereas Hystrix focuses primarily on client-side resilience features without the centralized control plane provided by Istio.

5. **Cross-Service Communication**:
Istio provides tools for managing cross-service communication such as traffic control, load balancing, and security policies at the network level, while Hystrix focuses on handling communication resilience within individual services through circuit breakers and fallback mechanisms.

6. **Granularity of Control**:
In Hystrix, developers have granular control over how each individual service handles faults and latency, while Istio offers a more centralized approach to managing service communication and resilience, providing a higher level of abstraction for developers. 

In Summary, Hystrix focuses on individual service resilience with client-side library features, while Istio provides a platform-agnostic service mesh solution for managing service communication at the network level.