Why should you care?

If you store dates as strings you sort them wrong and miss timezone truth. BSON Date and ObjectId give correct types for queries and indexes.

See it live — copy this example

Open mongosh or MongoDB Compass, select database nosqlverse, then run the example. Change one field and run again.

db.orders.insertOne({
  _id: ObjectId(),
  total: NumberDecimal("1999.50"),
  placedAt: ISODate("2026-07-19T10:00:00Z"),
  meta: BinData(0, "QQ==")
})
db.orders.findOne({}, { placedAt: 1, total: 1 })

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

What happened?

• ObjectId is MongoDB’s default unique id type.
• NumberDecimal keeps money precise.
• ISODate stores a real date, not a string.
• BinData holds binary.

Practice next

1. Insert the sample order in mongosh.
2. Run typeof checks mentally: placedAt should be a Date in the shell.
3. Compare with inserting placedAt: "2026-07-19" as a string — note the type difference.
4. Insert with total: 1999.5 (double) vs NumberDecimal and compare.
5. Run db.orders.find({ placedAt: { $type: "date" } }).

Remember

JSON is for interchange; BSON is MongoDB’s storage format. BSON adds Date, ObjectId, Decimal128, and more. Prefer real BSON types for dates and money.

Invoice totals that must match accounting

An e-commerce backend stores order.total as Decimal128 so ₹1999.50 does not become 1999.499999.

Outcome: Finance exports match the UI to the paisa.