* the cache; the cache may delete or overwrite files from its directory. It is an error for
 * multiple processes to use the same cache directory at the same time.
 *
 * This cache limits the number of bytes that it will store on the filesystem. When the number of
 * stored bytes exceeds the limit, the cache will remove entries in the background until the limit
 * is satisfied. The limit is not strict: the cache may temporarily exceed it while waiting for