Add an implicit dependency

Implicit dependencies (references) — the default

When one resource references another's attribute, Terraform infers that it must come second:

resource "demo_server" "web" {
  network_id = demo_network.main.id   # ← reference
}

Because web uses demo_network.main.id, Terraform knows the network must exist first. You didn't declare an order — the reference is the order:

demo_network.main: Creating...
demo_network.main: Creation complete
demo_server.web: Creating...
demo_server.web: Creation complete

It has to be: the network's id doesn't exist until the network does. This is the idiomatic way to sequence resources, and it's self-documenting: the dependency is visible right where the value is used.