During September 2025, Alex Klotz developed Precompiled Header (PCH) support for Buck2 C++ builds, contributing to both the facebook/buck2-prelude and facebook/buck2 repositories. He implemented new rules and integrated PCH generation and consumption into the existing C++ compilation logic, targeting faster local builds by reducing redundant header recompilations. Working primarily in C++ and Python, Alex focused on build systems and compiler internals to ensure maintainability and performance optimization. His work established a technical foundation for broader performance improvements, demonstrating depth in rule-based extension and a clear understanding of the complexities involved in large-scale C++ build infrastructure.