The article provides a comprehensive overview of Bazel, a build automation tool, emphasizing its capabilities for managing scalable builds and testing processes across various programming languages. It highlights Bazel's efficiency in handling incremental builds by allowing developers to rebuild only the changed parts of the code, thereby improving build performance compared to other tools like Make. The article guides readers through implementing a simple Python and Flask application using Bazel, detailing steps such as setting up the folder structure, creating the WORKSPACE and BUILD files, coding a calculator app and its unit test, and running the application. Additionally, it introduces Earthly as a complementary tool for creating reproducible builds by leveraging containers, comparing its approach to Bazel’s build system. The article concludes by showcasing a practical example of using Bazel to build and test a Python application, underscoring its utility in managing complex software projects.