Docker image building can be time-consuming, particularly for larger applications with many dependencies. To speed up Docker image building, developers can use a `.dockerignore` file to ignore unnecessary files and directories, reducing the size of the build context and resulting in faster builds. Additionally, using a dependency lockfile can ensure deterministic builds and optimize build performance by leveraging Docker's caching mechanism. Furthermore, grouping commands based on their likelihood to change can help save time and resources during the Docker image rebuilding process. By incorporating these strategies into their workflows, developers and DevOps teams can improve the efficiency of their CI pipelines, reduce costs, and enhance the security posture of their applications.