ROS2’s interface generation can be a major bottleneck in the build process, especially for large projects. The rosidl toolchain, while reliable, is slow due to its Python-based code generation and inefficient use of CPU resources. rosidlcpp (https://github.com/TonyWelte/rosidlcpp) tackles these challenges by reimplementing the rosidl generators in C++. However, switching to C++ is only one of the ways rosidlcpp achieves faster builds. This talk will walk through the optimization journey behind rosidlcpp. We’ll cover how the build inefficiencies were diagnosed and the techniques used to address them.