insertOne() — MongoDB Technical Interview Questions & Answers

Inserts a single document into a collection.

insertOne()

  • Simple meaning: insertOne adds one document. Mongo adds _id if you omit it.
  • How to use: db.students.insertOne({ name: "Asha", roll: 12, city: "Pune", marks: 72 })
  • Result: { acknowledged: true, insertedId: ObjectId("...") }.
  • Try this: insert Asha, then db.students.find().
  • Common mistake: insertOne([ {...}, {...} ]) — that is insertMany. Or forgetting quotes on keys in some drivers.
  • Interview tip: One doc, auto _id, returns insertedId.

Technical Interview Tip: Show insertOne with name, roll, marks.

Code Examples for insertOne()

insertOne() — working example

db.users.insertOne({
  name: "Ada",
  email: "ada@example.com",
  age: 36,
  city: "Pune",
  skills: ["Java", "MongoDB"],
  active: true
})

insertOne() — insertOne adds a single BSON document; MongoDB assigns ObjectId _id if missing.

How to Explain insertOne() to an Interviewer

What does insertOne return?

acknowledged and insertedId