To optimize the execution time of XCUITest on iOS simulators, the article demonstrates how to leverage CircleCI's features such as test splitting and parallelism in conjunction with fastlane. As iOS application code expands, automated tests can significantly extend CI/CD build times, thereby slowing development. By using CircleCI, developers can reduce execution time through multiple resource classes, dependency caching, and parallel test runs. The tutorial outlines steps like pre-building tests, running them on multiple macOS VMs, and utilizing timing-based test splitting for efficient distribution across parallel environments. This approach not only minimizes test execution time but also enhances cost efficiency, as CircleCI charges based on macOS VM usage rather than parallelism. The method is particularly useful for improving performance in iOS application development.