RBAC vs ABAC vs ReBAC: How to Choose and Implement Access Control Models

Introduction With the shift toward microservices and the widespread adoption of multi-tenant SaaS, requirements that cannot be expressed by traditional access control are rapidly increasing. Have you ever heard the term Role Explosion? RBAC alone is not enough. So, is ABAC the answer? Or ReBAC, which we hear a lot about lately? What exactly is the difference? In this article, we will compare three access control models—RBAC, ABAC, and ReBAC—by looking at practical policy examples from actual products (AWS IAM, Kubernetes, Cedar, OpenFGA, and SpiceDB). 1. RBAC — Role-Based Access Control 1.1 The Basic Structure of RBAC Let's start with RBAC. It is the simplest model and likely the first one everyone encounters. What it does is straightforward: Assign roles to users, and assign permissions to roles. Users do not hold permissions directly; they acquire them through their roles. The reasons this became so widespread are: For a new user, you only need to assign one role. If you ask, "Who ha