code: function processAcknowledgement(acknowledgement, callback) {
    var datasetId = acknowledgement.datasetId;
    if (!datasetId || !acknowledgement.cuid || !acknowledgement.hash) {
      debugError("acknowledgement missing info %j", acknowledgement);
      return callback();
    }
    debug('processAcknowledge :: processing acknowledge %j', acknowledgement);
    syncStorage.findAndDeleteUpdate(datasetId, acknowledgement, function(err) {
      if (err) {
        debugError('END processAcknowledge - err=%s', err);
        return callback(err);
      } else {
        debug('acknowledgement processed successfully. hash = %s', acknowledgement.hash);
        return callback();
      }
    });
  }
docs: Process a single acknowledgement. It will find the acknowledgement in the <datasetId>-updates collection and remove it.
  @param {Object} acknowledgement represent the result of a sync update operation
  @param {String} acknowledgement.datasetId the dataset id
  @param {String} acknowledgement.cuid the unique client id
  @param {String} acknowledgement.hash the hash value of the acknowledgement
  @param {any} callback