Write concern and data durability in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the write concern to acknowledge writes on the primary only.

MongoDB

db.collection.insertOne({name: 'Alice'}, {writeConcern: {w: [1])

Drag options to blanks, or click blank then click option'

A1

B0

Cmajority

Dall

Attempts:

3 left

💡 Hint

Common Mistakes

Using w: 0 causes no acknowledgment and no guarantee of durability.

Using w: majority waits for multiple nodes, not just primary.

Setting w: 1 means the write is acknowledged by the primary only.

2fill in blank

medium

Complete the code to ensure the write is acknowledged by the majority of replica set members.

MongoDB

db.collection.insertOne({score: 100}, {writeConcern: {w: "[1]"}})

Drag options to blanks, or click blank then click option'

A0

B1

Cmajority

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using w: 1 only waits for primary, not majority.

Using w: 0 means no acknowledgment.

Using w: 'majority' ensures the write is confirmed by most nodes, increasing durability.

3fill in blank

hard

Fix the error in the write concern option to wait for journaling confirmation.

MongoDB

db.collection.insertOne({item: 'book'}, {writeConcern: {w: 1, j: [1])

Drag options to blanks, or click blank then click option'

Atrue

Bfalse

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using j: false disables journaling acknowledgment, risking data loss.

Using j: 1 or 0 is invalid; it must be boolean true or false.

Setting j: true waits for the write to be committed to the journal, ensuring durability.

4fill in blank

hard

Fill both blanks to set write concern to wait for 2 nodes and enable journaling.

MongoDB

db.collection.insertOne({status: 'active'}, {writeConcern: {w: [1], j: [2])

Drag options to blanks, or click blank then click option'

A2

Btrue

Cfalse

Dmajority

Attempts:

3 left

💡 Hint

Common Mistakes

Using j as a number instead of boolean.

Using w as 'majority' when number 2 is required.

Setting w: 2 waits for acknowledgment from 2 nodes, and j: true waits for journaling.

5fill in blank

hard

Fill all three blanks to set write concern with majority, journaling enabled, and a timeout of 5000 ms.

MongoDB

db.collection.insertOne({task: 'backup'}, {writeConcern: {w: "[1]", j: [2], wtimeout: [3])

Drag options to blanks, or click blank then click option'

A1

Btrue

C5000

Dmajority

Attempts:

3 left

💡 Hint

Common Mistakes

Using wtimeout as a boolean or string instead of a number.

Setting j to false disables journaling.

Using w: 'majority' waits for most nodes, j: true enables journaling, and wtimeout: 5000 sets a 5-second timeout.