Zanzibar: Google’s Consistent, Global Authorization System

This paper presents the design, implementation, and deployment of Zanzibar, a global system for storing and evaluating access control lists. Its authorization decisions respect causal ordering of user actions and thus provide external consistency amid changes to access control lists and object contents. Zanzibar scales to trillions of access control lists and millions of authorization requests per second to support services used by billions of people.

Source: ai.google