Mapp (Messenger App) is a full-stack real-time messaging application built with React, FastAPI, PostgreSQL, and WebSockets. It provides authenticated one-to-one messaging with JWT-based identity, persistent conversation history, unread message tracking, and real-time message delivery. The application is containerized using Docker and Docker Compose, with Nginx serving the frontend and routing API and WebSocket traffic to the backend, demonstrating a complete modern application architecture from user authentication and data persistence to real-time communication and deployment.