The article details the implementation of a secure, user-specific access control model for a social network utilizing PostgreSQL's Row-Level Security (RLS) and the Drizzle ORM. The setup, inspired by Twitter's data model, includes tables for users, profiles, posts, comments, chats, and chat participants, each with specific RLS policies to control access and modifications. The users table is restricted to admin access for synchronization, while the user_profiles table allows users to update their own profiles and view others. Posts and comments allow authors to modify their own content, with public visibility for all. The chat system is more complex, relying on a view to manage participant visibility without recursion issues, ensuring only participants can see chat details, while messages can only be inserted by participants. The article highlights the challenges of writing RLS policies, emphasizing the need for thorough validation to prevent data leaks and suggesting that much of the access logic should reside in the database layer for security.