Architecture
Open API
https://swagger.io/docs/specification/about/
AWS API Gateway
The AWS API Gateway is a managed service that provides for a L7 reverse proxy, SSL termination, Authentication - it works with a WAF.
Azure
The Azure Application Gateway https://docs.microsoft.com/en-us/azure/architecture/microservices/design/gateway is a managed load balancer that provides for a L7 reverse proxy, SSL termination and WAF functionality.
Azure API Management works with the Azure AG to publish API specifications
Kubernetes Ingress Controller
Envoy Kubernetes API Gateway
https://www.envoyproxy.io/docs/envoy/latest/start/distro/ambassador
https://www.consul.io/docs/platform/k8s/run.html
Consul Service Mesh
https://www.consul.io/intro/index.html
Commercial
3Scale - Redhat
Links
https://www.nginx.com/blog/building-microservices-using-an-api-gateway/