Orphaned Resource
Infrastructure that is billed but serves nothing, typically left behind when the thing it supported was deleted.
The cheapest savings available, requiring no architectural change and no trade-off, and routinely worth several percent of a cloud bill.
The recurring categories: unattached storage volumes from terminated instances; unassociated static IP addresses, which are charged precisely because they are idle; old snapshots and machine images accumulating from automated backup jobs nobody reviews; load balancers with no healthy targets; idle databases created for a project that ended; incomplete multipart uploads, billed and invisible in an ordinary object listing; and non-production environments running overnight, at weekends and through holidays — which alone is often the single largest item.
Finding them is a scheduled report, not a heroic exercise. Most providers surface several categories directly.
What makes elimination durable rather than a one-off sweep:
Delete by default with a grace period — automated cleanup of resources untagged or unattached beyond a threshold, with notification before deletion.
Scheduled shutdown for non-production, which is a configuration change with no downside.
Ownership tags enforced at creation, so an orphan has a name attached when it is found.
Recurring review, because waste regenerates continuously and a single campaign's savings decay within a year.