mongodb vs filedb

filedb.ts

import fs from "fs";

const n = 5000000;
const s = [];
for (let i = 0; i < n; i++) {
  s.push({
    idx: i,
  });
}

const beforeWrite = Date.now();
fs.writeFileSync("data.json", JSON.stringify(s));
const afterWrite = Date.now();
const b = fs.readFileSync("data.json");
const afterRead = Date.now();
const writeTime = afterWrite - beforeWrite;
const readTime = afterRead - afterWrite;
console.log(
  `Writing/Reading ${n} objects to filedb took ${writeTime}/${readTime} ms`
);

mongodb.ts

import { MongoClient } from "mongodb";
// TODO: use mongoose
const uri = "mongodb://localhost:27017";
const client = new MongoClient(uri);

async function run() {
  try {
    await client.connect();
    const database = client.db("scratch");
    const scratch = database.collection("scratch");
    await scratch.deleteMany({});

    const n = 5000000;
    const s = [];
    for (let i = 0; i < n; i++) {
      s.push({
        idx: i,
      });
    }
    const beforeWrite = Date.now();
    const result = await scratch.insertMany(s);
    const afterWrite = Date.now();
    const cursor = scratch.find({});
    await cursor.forEach(() => {});
    const afterRead = Date.now();
    const writeTime = afterWrite - beforeWrite;
    const readTime = afterRead - afterWrite;
    console.log(
      `Writing/Reading ${n} objects to filedb took ${writeTime}/${readTime} ms`
    );
  } finally {
    await client.close();
  }
}
run().catch(console.dir);

Results:
Writing/Reading 5000000 objects to filedb took 846/26 ms
Writing/Reading 5000000 objects to mongodb took 24082/8239 ms

Of course mongodb can retrieve a document in O(1) though, whereas filedb takes O(n)