Performance comparison between mongoose `Document#save(...)` and `Model.bulkSave(...)`

mongoose.save.vs.bulk.save.js

import mongoose from 'mongoose';
const { Schema } = mongoose;

const ALL_BANK_ACCOUNTS_COUNT = 100_000;

start().catch(console.error);

async function start () {
  await runExperiment(bulkSaveDocuments);
  await runExperiment(saveDocumentsIndividually);
}

async function runExperiment (savingFunction) {
  await prepareDatabase();

  const BankAccount = generateBankAccountModel();

  const newBankAccountsToCreate = createEmptyArrayWithLength(ALL_BANK_ACCOUNTS_COUNT / 2).map(() => {
    return new BankAccount({ balance: generateRandomInteger(0, 100) });
  });

  const bankAccountsToUpdate = createEmptyArrayWithLength(ALL_BANK_ACCOUNTS_COUNT / 2).map(() => {
    return new BankAccount({ balance: generateRandomInteger(0, 100) });
  });

  await BankAccount.insertMany(bankAccountsToUpdate);

  bankAccountsToUpdate.forEach((bankAccount) => {
    bankAccount.balance = generateRandomInteger(0, 100);
  });

  const allBankAccountsDocuments = [
    ...newBankAccountsToCreate,
    ...bankAccountsToUpdate
  ];

  const timestampBeforeSaving = Date.now();

  await savingFunction(allBankAccountsDocuments, BankAccount);

  const timestampAfterSaving = Date.now();

  console.log(`Time elapsed for ${savingFunction.name} is ${timestampAfterSaving - timestampBeforeSaving}ms.`);
}

async function prepareDatabase () {
  await mongoose.connect('mongodb://localhost:27017/test');
  await mongoose.connection.dropDatabase();
}

function generateBankAccountModel () {
  if (mongoose.models.BankAccount) {
    return mongoose.models.BankAccount;
  }

  const bankAccountSchema = new Schema({ balance: Number });

  const BankAccount = mongoose.model('BankAccount', bankAccountSchema);
  return BankAccount;
}

async function bulkSaveDocuments (documents, Model) {
  await Model.bulkSave(documents);
}

async function saveDocumentsIndividually (documents) {
  await Promise.all(documents.map(async (document) => {
    await document.save();
  }));
}

function createEmptyArrayWithLength (desiredLength) {
  const arr = Array.from({ length: desiredLength });
  return arr;
}


function generateRandomInteger (min, max) {
  return Math.floor(generateRandomFloat(min, max));
}

function generateRandomFloat (min, max) {
  return Math.random() * (max - min) + min;
}

output.txt

Time elapsed for bulkSaveDocuments is 12141ms.
Time elapsed for saveDocumentsIndividually is 31323ms.