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 minimizing redundant header recompilations. His work required deep understanding of build systems, compiler internals, and performance optimization, utilizing C++, Python, and Bzl. By establishing a maintainable foundation for PCH handling, Alex enabled broader performance improvements across the codebase. The engineering demonstrated thoughtful integration and technical depth, addressing both efficiency and maintainability in complex build environments.