Nginx proxy_pass for /api/ - nginx

Question

I am currently deploying a ReactJS app to a Nginx server. The backend the application is located in a private network. I am currently using http://my-domain.com/ to access the frontend and from the frontend I access the backend using http://my-domain.com/api/. I am trying to configure Nginx to pass from http://my-domain.com/api/ to http://my-backend-loadbalancer.com/api/.
This is the configuration that I am running from `/etc/nginx/sites-available/my-domain.com
server {
listen 80;
listen [::]:80;
root /var/www/my-domain.com/html;
index index.html index.htm index.nginx-debian.html;
server_name www.my-domain.com my-domain.com;
location / {
try_files $uri $uri/ =404;
}
location /api/ {
proxy_set_header Host my-backend-loadbalancer.com;
proxy_pass http://my-backend-loadbalancer.com$is_args$args;
}
}
I get a Bad Request error with this approach. I would like to know if I am following good practices in terms of accessing a backend within a private network and how can I make this work.
UPDATE
I have tried this configuration, but it seems that is not passing the arguments. Because when I try http://my-domain.com/api/ it redirects to http://my-backend-loadbalancer.com whit out any argument on it.
server {
listen 80;
listen [::]:80;
root /var/www/my-domain.com/html;
index index.html index.htm index.nginx-debian.html;
server_name www.my-domain.com my-domain.com;
location / {
try_files $uri $uri/ =404;
}
location /api/ {
proxy_pass http://my-backend-loadbalancer.com;
}
}
Here's what I found in error.log.
2022/11/04 15:57:52 [error] 4749#4749: *3 no resolver defined to resolve internal-backend-213123123.us-west-1.elb.amazonaws.com, client: 10.0.0.78, server: www.my-domain.com, request: "GET /api/ HTTP/1.1", host: "my-domain.com", referrer: "http://my-domain.com/"