code: function initializeKVPersistent (config) {
  	/* NB Makes FS syscalls each time in case config changes during lifetime.
  	 * Could cache the set of initialized dirs if this is a performance issue. */
  
  	/* First try a mkdir. Dir might exist already. */
  	try {
  		fs.mkdirSync(config.cache.persistentDir);
  	} catch (e) {
  	}
  
  	/* If we have a dir now, we're happy.
  	 * This also works if persistentDir is a symlink. */
  	try {
  		const stats = fs.lstatSync(config.cache.persistentDir);
  		if (stats.isDirectory()) {
  			return true;
  		} else {
  			return false;
  		}
  	} catch (e) {
  		/* Hmm. */
  		return false;
  	}
  }
docs: /* Persistent KV. /* Returns true if initialized, false on initialization failure.