railway's redis is unmanaged ,it runs from the official Redis Docker image and you have full control over configuration. However, installing new relic directly into it isn't straightforward because  there's no shell/SSH access to the running container.The easiest path is monitoring redis through your backend's New Relic APM agent rather than installing anything into the redis instance itself or integrate a prometheus redis exporter as a sidecar service for metrics.
docs: https://docs.railway.com/databases/redis

Got it, thank you