What Docker is and how it's different from a VM, then images, containers, Dockerfiles, volumes, networking, and Compose — through to multi-stage builds and image security.
What CMake actually generates, targets and the PUBLIC/PRIVATE/INTERFACE model, dependencies, CTest — through to presets, cross-compiling, and packaging with CPack.
A general method for finding bugs — gdb, Python's pdb, reading stack traces and core dumps, binary-search debugging, and when print statements beat a debugger.
Finding out where the time actually goes — time, perf, Python's cProfile and py-spy, memory profiling, and reading a flame graph.
More on this hub soon — testing strategy and CI basics. For GPU-specific profiling (Nsight, rocprof), see the GPU optimization page.