No Trafiek doesn’t need Redis, but your NodeJS web site might. So when you enable Redis it is used in NodeJS for sessions for example. However when also Traefik is enabled, all the docker services like web and db are placed in special network proxy so that are isolated from the rest of the world and only accessible via Traefik and each other. But Redis wasn’t placed in the same network so that is why it wasn’t accessible even if it was running and also the web service couldn’t find Redis and NodeJS was crashing.
So placing also Redis in the same network solve all the problems.