Authorization service

Design an authorization service that answers 'can user U do action A on resource R?' for a collaboration platform with 100M users and deeply nested resource hierarchies (orgs to teams to folders to documents) plus per-resource sharing. It must serve 1M authorization checks/sec at p99 under 10ms, reflect a permission change (e.g., a revoked share) within ~1s, and never return a false-allow. Discuss the data model, how you evaluate nested/inherited permissions at scale, and the consistency trade-off.