Recently I ran into a situation where I wanted to proxy the calls made by a client application (i.e. javascript AJAX calls) for a web application that was hosted on another machine. So the configuration looked something like below: https://www.mywebsite.com -> user machine (javascript) -> https://api.mywebsite.com/api-1/endpoint I didn't want to run "www.mywebsite.com" code on my machine, I wanted to run the deployed website in my browser, but I wanted all calls to "api.mywebsite.com/api-1" to be routed to my local development environment so I could either debug or mock the API responses as I wanted. The solution comprised of 3 basic elements:
  1. An Nginx reverse proxy running in Docker on my machine
  2. Self signed SSL certificates for TLS termination in Nginx
  3. Running Chrome with custom host resolver rules (this could also be done in /etc/hosts but I only wanted a temporary solution)
If your API calls don't use HTTPS then you don't need the TLS termination, but in my case I do need it so I created some self-signed certificates that I will later trust within Chrome: 
sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout nginx-selfsigned.key -out nginx-selfsigned.crt
Now create a reverse-proxy Nginx configuration file, like below: 

server {
    listen 0.0.0.0:80;
    listen 0.0.0.0:443 ssl;
    server_name host.docker.internal;
    ssl_certificate       /etc/ssl/certs/server.crt;
    ssl_certificate_key   /etc/ssl/certs/server.key;
    location /api-1/ {
        proxy_pass http://host.docker.internal:5001/;
    }
}
This essentially now routes the traffics from "https://localhost/api-1" to "http://host-machine:5001/" which is where I can run the development mode API. With those things in place, whenever I want to the run the deployed website against my local machine APIs, I can use the below commands: 

docker run --rm \
-p 80:80 -p 443:443 \
--name nginx-reverse-proxy \
--add-host=host.docker.internal:host-gateway \
-v $(pwd)/nginx.conf:/etc/nginx/conf.d/default.conf \
-v $(pwd)/nginx-selfsigned.crt:/etc/ssl/certs/server.crt \
-v $(pwd)/nginx-selfsigned.key:/etc/ssl/certs/server.key \
nginx &
google-chrome https://www.mywebsite.com/ --host-resolver-rules="MAP api.mywebsite.com 127.0.0.1"
The first time you run it, Chrome won't trust your SSL certs, but if you open an API URL in a new tab and manually trust it, then the clientside calls will work :)