The optimal solution to prevent overwriting changes in a collaborative Databricks project is to implement version control using Git within the Databricks workspace. Git provides a centralized repository for storing and tracking all notebook versions, enabling team members to view the change history, revert to previous versions if necessary, and avoid conflicts. It supports branching and merging workflows for parallel development and controlled integration of contributions, thus preventing accidental overwrites and facilitating code review before merging changes into the main notebook. Databricks' seamless integration with Git allows for direct version control within the workspace, with the ability to connect notebooks to Git repositories and push or pull changes directly from the UI. Other options like enabling “Auto-Save“, sharing a common username and password, or using the “Lock“ feature are either insufficient for preventing conflicts, insecure, or hinder collaboration, making Git version control the most comprehensive and collaborative approach for managing changes in shared notebooks.