The article describes how Slack improved its build pipeline for Quip and Slack Canvas, reducing build times from 60 minutes to a significantly faster rate. This change was essential for enhancing the agility of their development process. By integrating advanced build tools like Bazel with established software engineering practices, the team was able to optimize performance through caching and parallelization. The authors explain the importance of structuring builds as directed acyclic graphs, where each build step has defined inputs, outputs, and transformation commands. This structure allows for better caching strategies. For example, caching the results of a factorial function improves performance by avoiding repeated calculations. The article emphasizes that for caching to be effective, functions need to be hermetic and idempotent, ensuring consistent outputs for the same inputs. Parallelization is another key strategy discussed. By dividing tasks across multiple CPU cores, the team can process images concurrently, significantly speeding up operations. However, this approach requires careful management of inputs and outputs to handle potential variations in order and results. The article highlights the importance of defining granular units of work to maximize both cache hit rates and parallel processing efficiency, ultimately achieving a more responsive build system.