Nginx as reverse proxy and load balancer

A reverse proxy sits in front of your app. It accepts requests from the internet and passes them to the app on a private port. Nginx is the common choice.

It handles TLS, serves static files such as images quickly, and adds headers such as X-Forwarded-For so the app knows the real visitor's address. With an upstream block it also works as a load balancer, spreading traffic across several copies of the app.

A minimal site is a server block with server_name, listen 443 ssl and location / { proxy_pass http://127.0.0.1:3000; }. Always run nginx -t to test the config before reloading, so a typo does not take the site down. A cloud load balancer or a Kubernetes ingress does the same job later, so the ideas carry over.