Building a simple event app from scratch involves creating a lean architecture that supports fast iteration and scalability, focusing on core features such as event creation, user registration, and real-time communication. Integrating PubNub’s real-time APIs allows for instant updates on RSVP statuses, live schedule changes, and attendee interactions, while a modular monorepo setup enhances development velocity. A systematic approach requires defining data models, establishing backend services for CRUD operations, and developing a responsive UI. Utilizing a tech stack that includes React for the frontend, Node.js with Express for backend logic, and Firebase for authentication and data storage ensures a robust foundation. PubNub enhances interactivity through real-time data synchronization and notifications, enabling features like live updates, attendee tracking, and in-app chat. Rapid deployment and iteration can be achieved by using platforms like Vercel or Netlify for CI/CD workflows and edge-optimized performance, with serverless functions simplifying backend logic. The app's UI/UX should prioritize clarity and speed, utilizing component libraries for design consistency and tools like React.memo for performance optimization, while PubNub's SDK facilitates real-time capabilities without extensive server infrastructure.