There's a moment where you launch a single EC2 instance and SSH just won't connect. You've even opened the security group to 0.0.0.0/0, and still nothing. You peer into the route table and there's no path to the internet gateway. This one-line mystery is the rite of passage everyone goes through when they first meet a VPC. A single missing route, and the entire traffic flow is blocked — this is the double edge of the determinism a VPC gets from being built on top of SDN (Software Defined Networking). "Deterministic" means "predictable," but it also means "get one line wrong and it breaks consistently."