Explore techniques for optimizing CI performance and reducing developer waiting time in this 28-minute RubyConf 2021 talk. Dive into Shopify's strategies for managing a massive and rapidly growing test suite of over 170,000 Ruby tests. Learn about monitoring, test selection, timeouts, and applying the 80/20 rule to improve CI efficiency. Discover data-driven development approaches, test suite optimization techniques, and methods for maintaining stability while scaling. Gain insights on using mapping to run tests related to PR changes, handling dynamic languages and meta-programming, and leveraging ActiveSupport Notifications. Understand how to compare and evaluate test performance based on factors like failure rate, complexity, churn, and coverage. Get inspired to experiment with load testing and incrementally improve your CI process for happier, more productive developers.