Consistency is the Key to Performance and Safety

The Zanzibar paper presents a revolutionary approach to permissions management by combining strong consistency, performance, and scalability into one global solution called "Zanzibar." To address the challenge of maintaining both consistency and caching, SpiceDB allows for some staleness in permissions requests while ensuring that the maximum possible staleness is acceptable. The concept of a ZedToken (or Zookie) was introduced to encode the minimal point-in-time at which cache results are considered valid. Additionally, SpiceDB offers per-request configurable consistency levels to accommodate different permission requirements.