Bazel projects typically start with the command `bazel build //...`, which builds everything in the workspace, but this approach can become inefficient as projects scale. To enhance efficiency, selective builds are recommended, focusing only on the necessary targets for each commit. This hands-on guide demonstrates how to use Bazel with Buildkite to create a dynamic and adaptable CI pipeline that leverages Git and Python to determine which Bazel targets to build, based on changes in the repository. By integrating Bazel's querying capabilities with a Buildkite pipeline defined in Python, users can achieve more granular control over builds, dynamically generate pipelines based on code changes, and improve build visibility through detailed annotations. This approach moves away from static YAML configurations, offering a more flexible and efficient solution for managing complex build processes.