The code below is working properly but how do I make this code faster and more efficient. How do I perfect this code?

Let's assume I have 1000 country, state and city records in a mongodb collection. I want to retrieve all the city data by matching country id and state id. Please tell me the perfect way to code.

// @route   GET citylist/:countryid/:stateid
// @desc    get all the city from mongodb for countryid and stateid

router.get("/citylist/:countryid/:stateid", (req, res) => {
  const isValidCountryid = mongoose.Types.ObjectId.isValid( req.params.countryid);
  const isValidStateid = mongoose.Types.ObjectId.isValid(req.params.stateid);

  if (isValidCountryid && isValidStateid) {
      country_id: req.params.countryid,
      state_id: req.params.stateid

      .then(cities => {
        if (!cities || !cities[0]) {
          return res.status(404).json({ msg: "City not found" });
        } else {
      .catch(error => res.status(500).send(error));

  } else {
    res.json({ msg: "Country or State Id is not valid" });

how to make this code highly fast, efficient, great time complexity and perfect way of code.

  • 1
    \$\begingroup\$ Please have a look at Titling your question in the Help center and change your title accordingly! Namely, describe what your task is, not what you expect from the review. \$\endgroup\$ – AlexV May 16 at 8:18

From a short review,

  • Make sure that your database has an index: https://docs.mongodb.com/manual/indexes/
  • For the 404, since most countries have more than 1 country, I would return "Cities not found", I might even include the provided country and city in the return message so that the admin can be provided with an informative message
  • I would have 2 different messages when the input data is bad, one for City, and one for country. Furthermore, for bad input data, I would use return code 400.
  • It's very minor, but CountryId looks better than countryid
  • Instead of if (isValidCountryid && isValidStateid) { I would check for bad data, and exit immediately, it makes for a lower cyclomatic complexity

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