Google Zanzibar is a large-scale authorization system that became the reference design for modern relationship-based access control. Instead of hard-coding permissions into each application, Zanzibar models access as relationships between users, resources, and roles, then evaluates whether a request should be allowed from that graph of facts.
This matters in cyber security because authorization is often the last gate before sensitive data or actions are exposed. Zanzibar-style systems let organizations enforce fine-grained permissions at cloud scale, but they also make policy data a critical security asset. If relationship tuples, policy rules, or synchronization are wrong, users may gain access they should not have, or legitimate access may fail. Defenders use Zanzibar-inspired designs to centralize authorization, separate it from business logic, and add auditing, testing, and rollback around permission changes.