C100DEV CRUD Operations Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  db.inventory.insertOne({ item: 'canvas', qty: 100 })

  Why this is correct

  insertOne inserts a single document and returns an InsertOneResult object that includes the acknowledged flag and the insertedId field. This gives the developer immediate access to the generated _id without an extra query, which is exactly what the scenario requires for a single-document insert.

• ✗

  db.inventory.update({ item: 'canvas' }, { qty: 100 }, { upsert: true })

  Why it's wrong here

  The update method is deprecated in favor of updateOne and updateMany, and it does not return the inserted _id in the same direct manner. Using upsert for a plain insert conflates two operations and complicates error handling. It also requires a filter document, which is unnecessary when the goal is simply to insert and retrieve the new identifier.

• ✗

  db.inventory.insertMany([{ item: 'canvas', qty: 100 }])

  Why it's wrong here

  insertMany is designed for arrays of documents and returns an InsertManyResult containing an array of insertedIds. Although it can insert one document if passed a single-element array, it is not the intended method for a single insert and returns a collection of identifiers rather than a single insertedId, making it a poor fit for the stated requirement.

• ✗

  db.inventory.save({ item: 'canvas', qty: 100 })

  Why it's wrong here

  The save method is deprecated in modern MongoDB drivers and shell versions. It either inserts or replaces depending on whether _id is present, which introduces ambiguity, and it does not provide the same clear single-insert result shape. Using it for a straightforward insert is discouraged and may not be available in newer tooling.