Pennybase is a lightweight Backend-as-a-Service (BaaS) implemented in Go, featuring essential backend functionalities such as file-based storage, REST API, authentication, and role-based access control, all within under 1000 lines of code. It uses human-readable CSV files for data storage and includes easy-to-define schemas, making it simple to manage resources and permissions. The system is designed for extendability through hooks, allowing users to customize functionalities as needed.