Microservices API Gateway

Benefits: Instead of specific services, clients talk to the API gateway, which provides a client-specific API.

Drawbacks: Needs to be HA & managed. New services & APIs needs updating the gateway.

Off the shelf:

• Commercial:
• AWS API Gateway: Configure each request to a BE service that is an AWS Lambda function, an app http service or AWS service.
• AWS App load balancer: Basic routing to BE services. 
• Open-source product:
• Kong: nginx http based. Has plugins.
• Traefix: Go based. Integrate with service registries.
• Open-source framework:
• Netflix Zuul
• Spring Cloud Gateway
• Graph based technologies:
• Netflix Falcor: A Graph query implementation. Netflix started with Groovy API scripts in a monolithic architecture. Moved to an API modules using NodeJS & Docker, where scripts invoke an API gateway using Netflix Falcor. Falcor does declarative dynamic API composition & can invoke multiple services in a single request.
• Facebook GraphQL: a standard with clients & servers available in multiple languages, such as NodeJS, Java & Scala.
• Apollo GraphQL: JS/NodeJS implementation with useful extensions to GraphQL with a server & client.

Source: Microservices Patterns by Chris Richardson