UserSchema.statics.getByVkId = (data, next) ->
  User = mongoose.model('User')

  userData = data.response[0]
  User.findOne vkontakteId: userData.id, (err, user) ->
    return next(err) if err
    return next(message: 'provide user id') unless userData.id

    return(null, user)

в контроллере
router.post '', (req, res) ->
  UserSchema.getByVkId data, (err, user) ->
    return res.mongooseError(err) if err
    return res.status(403).json messages: ['user not found'] unless user

    ...