Their system utilizes nginx as a reverse proxy server to handle incoming traffic and route it to a custom-built application server, which is built on top of the Symfony framework. The application server contains several microservices that provide various functionalities such as authentication, payments, and user management. The frontend is built using React and Next.js, while the backend uses Node.js and Express.js for API development. This architecture allows for seamless integration with third-party services and a high degree of scalability and flexibility.