✗ A list of IP addresses in each caller's config file
✗ DNS records with a one-day TTL
✓A service registry fed by health checks (e.g. Consul, Kubernetes endpoints)Correct
✗ Broadcasting a request to the whole subnet
Why
Instances register (or are registered by the platform) and are removed when health checks fail. Callers, or a load balancer in front of them, read the registry, so the list stays current without redeploying anything.