EFS file systems that are no longer attached to any running services — such as EC2 instances or Lambda functions — continue to incur storage charges. This often occurs after workloads are decommissioned but the file system is left behind. A quick indicator of this state is when the EFS file system has no mount targets configured. Without active usage or connection, these orphaned file systems represent pure cost with no functional value. Unlike block storage, EFS does not require an attached instance to incur billing, making it easy for unused resources to go unnoticed.