code: function (_data, cb) {
        if(!db.data) return cb(new Error('kiddb not open'))
        if(!writing) return db._update(_data, cb)
        db.__data = _data
        qcb.push(cb)
        onWrote = function () {
          onWrote = null
          var cbs = qcb; qcb = []
          var _data = db.__data
          db.__data = null
          db.update(_data, function (err) {
            cbs.forEach(function (cb) {
              cb(err)
            })
          })
        }
      }
docs: instead of doing a concurrent write, queue the new writes. these can probably be merged together, and then a bunch will succeed at once. if you contrived your benchmark the right way, this could look like really great performance!