An access boundary is the point at which a system, account, or role should no longer be able to view or use data. It defines who can access particular resources and where that access ends—for example, separating a production archive from unrelated teams or systems.
Clear boundaries help limit exposure if an account is compromised, reduce accidental sharing, and keep old or sensitive assets available only to people who need them. In practice, defenders enforce them with permissions, role-based access controls, network segmentation, and regular access reviews. Forgotten archives and backups should be included: if access is broader than necessary, a leak or intrusion can expose data beyond its intended audience.