Oso is an authorization as a service company that provides enterprise-grade RBAC (Role-Based Access Control) without requiring changes to application architecture. It exposes an API that answers permissions-related questions, enabling integration across services with high availability and low latency. Oso allows the implementation of RBAC, ReBAC, and ABAC, supports local and cloud architecture, and enables developers to write authorization rules using Polar, its own domain-specific language (DSL). Its platform helps manage authorization efficiently across microservices, ensuring security and performance while reducing development time and complexity.