Write concern levels (w: 1, majority) in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the write concern level w: 1 mean in MongoDB?

It means the write operation is acknowledged by the primary node only. The operation is confirmed as saved on the primary before returning success.

intermediate

Explain the write concern level w: majority in MongoDB.

The write operation is acknowledged only after a majority of replica set members confirm the write. This ensures better data durability and consistency.

intermediate

Why would you choose w: majority over w: 1?

Choosing w: majority ensures data is saved on most nodes, reducing risk of data loss if the primary fails. w: 1 is faster but less safe.

beginner

What happens if you set write concern to w: 0?

The write operation is unacknowledged. The client does not wait for confirmation, so it is faster but you don't know if the write succeeded.

intermediate

How does write concern affect application performance and reliability?

Higher write concern levels (like w: majority) increase reliability but add latency. Lower levels (like w: 1) are faster but risk data loss.

What does w: 1 guarantee in MongoDB write concern?

A Write is unacknowledged

B Write is confirmed by all replica set members

C Write is confirmed by a majority of nodes

D Write is confirmed by the primary node only

w: 1 means the primary node confirms the write before success is returned.

Which write concern level waits for most replica set members to confirm the write?

A w: 0

B w: majority

C w: 1

D w: all

w: majority waits for a majority of nodes to confirm the write.

What is a risk of using w: 0 write concern?

A Slower writes

B Write waits for majority confirmation

C No confirmation of write success

D Data is saved on all nodes

w: 0 means no acknowledgement, so you don't know if the write succeeded.

Which write concern level provides the highest data durability?

A w: majority

B w: 1

C w: 0

D w: 0 with journaling

w: majority ensures data is saved on most nodes, improving durability.

If you want the fastest write speed and can tolerate some data loss, which write concern would you choose?

A w: 0

B w: 1

C w: majority

D w: all

w: 0 is fastest but does not confirm writes.

Describe the differences between w: 1 and w: majority write concern levels in MongoDB.

Think about how many nodes confirm the write and the tradeoff between speed and safety.

Explain how write concern levels affect data safety and application performance.

Consider the balance between speed and reliability.