Write concern basics 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'

A0

Bmajority

C1

Dall

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'majority' when only primary acknowledgment is needed.

Using 0 which means no acknowledgment.

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

2fill in blank

medium

Complete the code to set the write concern to require acknowledgment from the majority of replica set members.

MongoDB

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

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

Aall

B1

C0

Dmajority

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 instead of 'majority' for stronger write guarantees.

Using 0 which means no acknowledgment.

Setting w: 'majority' ensures the write is acknowledged by most nodes in the replica set.

3fill in blank

hard

Fix the error in the write concern option to wait for acknowledgment from two nodes.

MongoDB

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

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

Amajority

B2

C"two"

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string like 'two' instead of the number 2.

Using 'majority' when a specific number is required.

The value 2 means the write must be acknowledged by two nodes. It must be a number, not a string.

4fill in blank

hard

Fill both blanks to set write concern to wait for majority acknowledgment and a timeout of 5000 milliseconds.

MongoDB

db.collection.insertOne({name: "Dave"}, {writeConcern: {w: [1], wtimeout: [2])

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

Amajority

B5000

C1000

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a timeout value too low or too high.

Using numeric w instead of 'majority' for majority acknowledgment.

Setting w: 'majority' waits for most nodes, and wtimeout: 5000 sets a 5-second timeout.

5fill in blank

hard

Fill all three blanks to set write concern to wait for 3 nodes, enable journaling, and set a timeout of 2000 milliseconds.

MongoDB

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

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

Atrue

B2000

C3

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using string 'true' instead of boolean true.

Setting wtimeout too high or too low.

Setting w: 3 waits for three nodes, j: true enables journaling, and wtimeout: 2000 sets a 2-second timeout.