It was a release build just to be clear. Debug builds twice as fast (they have a custom profile with opt-level = 1) and indeed uses a lot more disk space. ram I just did a release build with –jobs=1, while measuring total RES memory of the cargo process tree. Number of pids ranged from 1 (just cargo, obviously) to 8, and max RES memory was ~3471MiB. So not too lightweight, but not buck breaking either. People just have unrealistic expectations. Developers could optimize the compiler for memory usage, but that would make the compiler actually slower. And who would be the target audience of such optimizations? People who want to build big Rust projects on Raspberry Pi Zero?