Please never hard code urls as that can only lead to issues.

can I see variables setup example for FE and BE that may be used for me to not try to hardcode urls to try to make it work at least somehow?

Of course! the template overview contains examples and explanations - https://railway.app/template/7uDSyj

Okay I tried to use variables - seems like it's taking it properly (required for me to rename all services), now I can access BE via /api, but FE still returning 502 dial tcp [fd12:eb49:f64::77:6dd6:aa39]:3000: connect: connection refused
How can I check what part my FE uses?

What port do you have it listening on?

Okay seems like I fixed all issues with port.

My fe app is made with create-react-app, so it's runned by scripts:
"scripts": {
"start": "react-scripts start",
"build": "CI=false react-scripts build",
"test": "react-scripts test",
"eject": "react-scripts eject"
},

start runned on Railway CI

I parametrized my FE app to try to resolve issues with host and port:
.env
REACT_APP_API_URL=process.env.API_URL
REACT_APP_PORT=process.env.PORT
REACT_APP_HOST=::

With my current configuration BE is available via /api. but when I try to access root url it redirects me to some ip address with port 80 and browser shows ERR_SSL_PROTOCOL_ERROR

Should I make some additional settings on my FE app to properly listen ipv6 and not be redirected? In logs of Caddy all okay - reuqest is handled

GET on root url gives 301 Moved Permanently

react-scripts start

This starts a development server, this is a far bigger issue than listening on IPv6.

I put together a create-react-app starter that runs a production ready web server - https://github.com/brody192/create-react-app-starter

Copy the nixpacks.toml and Caddyfile from this repo into your frontend project folder.

Brody, could you elaborate how development server is making my FE application not available in this particular configuration? It's non production environment of my app

Development servers are only meant to be used in a local development environment, you stick it in a production environment such as Railway (regardless of your intended use) things just don't work correctly, aside from the massive memory usage you would pay for with a development server.

Brody, I applied your configuration from https://github.com/brody192/create-react-app-starter

Accroding to logs now my FE app is driven by Caddy, but still behavior is the same - I have redirect to IP address

I googled similar behavior and solution was about tls_ondemand
https://caddy.community/t/reverse-proxy-is-changing-url-with-a-301-status/14828/3

Can you help me extend current configuration with that option? Should I change caddyfile in FE or I should modify reverse proxy config somehow?

You wouldn't want to do anything with TLS as that's something Railway handles for you.

Are you using the internal domain for the proxy configuration?

Yes!

Looks good, can you send me a link to where I can experience this redirect?

https://enot-admin-dev.up.railway.app/

Is there any chance it's cached response because of my previous misconfigurations?

Cache from your browser, yes, because I am not seeing any redirect, just getting a basic auth login prompt.

Wow it started work after resetting the browser cache! Brody thank you so much it was a life saver (and memory saver it eats 20 mb instead of 1000 now hahhahaha)

No problem, and yeah for sure you never want to be running development servers on Railway even if memory isn't a concern.