something.js

Something
  .findOne({
    where: {
      id: somethingId
    }
  })
  .then(function(something) {
    if (!something) {
      res.notFound('Something is not found.');
      return;
    }

    return doSomethingCool();
  })
  .then(function(resultOfSomethingCool) {
    return res.ok(resultOfSomethingCool);
  })
  .catch(function(err) {
    return res.serverError();
  });