If your key is a hash of the code and its dependencies, for a given toolchain and target, then any change to the code, its dependencies, the toolchain or target

If your key is a hash of the code and its dependencies, for a given toolchain and target, then any change to the code, its dependencies, the toolchain or target will result in a new key unique to that configuration. Though I am not familiar with these distributed caching systems so I could be overlooking something.