The Lunch Money web app is a personal finance tracking and budgeting tool that has gained popularity despite being developed by a team of one. Its success can be attributed to its use of the Jamstack architecture, which promotes decoupling front-end from back-end services, allowing for agility and confidence in development. The application's features include transaction tracking, budget analysis, and multi-currency support, all delivered through a user-friendly interface built with React and hosted on Netlify. Lunch Money's backend is provided by a mixture of third-party services and in-house services, leveraging NodeJS Express, Redis, and PostgresSQL. The application's decoupling enables easy iteration and updates, allowing for rapid deployment to production environments. Its use of the Jamstack architecture has enabled it to scale efficiently and achieve success as a solo project.