Delivery First companies like Airbnb, Uber, Elastic, and Slack achieve success by minimizing build times, allowing them to quickly deliver and iterate on software. This approach emphasizes efficient testing practices, where engineers write their own tests, predominantly unit tests, in contrast to the outdated waterfall method that relied on dedicated teams. As AI tools lower the cost of test creation, the volume of tests has increased, often leading to challenges with build times and the prevalence of flaky tests, which are unreliable and expensive to manage, especially in large organizations. Successful companies implement strategies like parallel test execution, test splitting, and feature flagging systems to maintain high-quality products and fast delivery. Buildkite’s Scale-Out Delivery Platform, featuring the Test Engine, offers advanced solutions for detecting and managing flaky tests, optimizing build times, and ensuring accountability and ownership in testing processes, supporting a Delivery First mindset.