As another data point - I ran the same llvm bazel build using remote build execution on 128 cores.

- clean, caching disabled @ 5.93m INFO: Elapsed time: 356.189s, Critical Path: 187.81s INFO: 4235 processes: 4235 remote.

- clean, fully remote cached @ 27.33s INFO: Elapsed time: 27.330s, Critical Path: 15.93s INFO: 4235 processes: 4235 remote cache hit.

Full disclosure - I co-founded BuildBuddy (YC W20) which provides bazel remote build execution and other open core bazel tooling