Qitian worked on performance optimization for error handling in the facebook/folly repository, focusing on the collectAllTryRange function. They implemented a co_awaitTry-based error handling mechanism to reduce exception unwinding overhead, while ensuring backward compatibility with SemiAwaitable types lacking co_awaitTry support. The approach included a compile-time has_co_awaitTry_v gate to select the optimal error handling path and maintained correctness without introducing overhead on successful executions. Qitian also developed benchmarks comparing the new method to traditional try/catch, quantifying error-path performance improvements. Their work demonstrated depth in C++ development, benchmarking, and performance optimization, addressing a targeted bottleneck with a robust solution.