On the Hobby plan, your $5/month subscription fee includes $5 of resource usage (CPU, memory, network egress, and volume storage), and you're only charged extra if your usage exceeds that amount. Whether your project crashes under 100 connections depends on your application's resource consumption and the per-service resource limits for the Hobby plan (up to 48 GB RAM, 48 vCPU per service). You can monitor your usage at railway.com/workspace/usage and set spending caps via cost control.