cacache is far too slow as a read and write cache to disk solution for hard-source.
On one test project on an older 13" MBP:
Instead of replacing, cacache will be an optional serializer like leveldb. Replacing append-serializer will fall to a new version of its idea. Instead of so finely trying to maximize use of append mode files, write out a log file once, with the meta info at the beginning and in a separate file additionally. Reading all the files in reverse builds up the prior state.