In the first part of a multi-part series on CPU time performance tuning for security software, the author focuses on identifying and mitigating high CPU usage issues, using a specific example on macOS. The article explains how to monitor CPU usage with tools like Activity Monitor and how to identify performance bottlenecks using macOS's spindump profiling tool. The example involves a demo program that experiences high CPU consumption due to the use of Apple's SecStaticCodeCheckValidityWithErrors function, a necessary but computing-intensive task, especially when validating large bundles like Xcode. The author demonstrates how changing a specific input parameter can significantly reduce CPU usage by avoiding the validation of bundle resources, although this introduces security trade-offs. The piece emphasizes the importance of carefully balancing performance improvements with potential compromises in security, and it hints at future discussions on other time-related performance topics in security software.