How to sync React frontend and Node backend using a single RBAC policy

A common pitfall in web security is maintaining separate authorization logic on the frontend and backend, which causes rules to drift out of sync when changes are made. Role-Based Access Control (RBAC) can be implemented using a shared policy engine that maps roles to resource-action permissions, running identically on both the server and in the browser. On the backend, middleware intercepts requests and enforces the policy before any controller logic executes, making server-side enforcement the true security boundary. On the frontend, the same engine drives UI decisions — hiding or disabling controls — ensuring the interface never offers actions the server would reject. Using a single source of truth for authorization rules, including conditional checks like ownership validation, eliminates inconsistencies across both enforcement points.