Does NginX(Open source, not Nginx plus), supports API Gateway?
Unfortunately the Nginx Api Gateway is featured only in Nginx Plus. But there is Kong, an alternative that is built on top of Nginx and is also open source.
There is even a post on Nginx's official blog about it: https://www.nginx.com/blog/nginx-powers-kong-api-management-solution/
Edit: The blog post has been replaced by an nginx plus one. The original post can still be accessed through web.archive.org:https://web.archive.org/web/20160413082936/https://www.nginx.com/blog/nginx-powers-kong-api-management-solution/