In the second part of a series on building a retrieval-augmented generation (RAG) application, Kevin Kimani guides on integrating Descope for authentication using SAML, implementing role-based access control (RBAC), and ensuring secure data handling through row-level security (RLS) with Supabase. The tutorial details creating a Descope SAML application, mapping roles to users, and configuring Supabase to enforce access controls using JSON Web Tokens (JWT). Additionally, it covers setting up a frontend with React, testing the application's role-based access, and deploying the app with considerations for security and scalability. Emphasizing the use of Descope, Supabase, and pgvector, the series provides a comprehensive framework for developing secure, scalable AI-powered applications.