Read concern levels (local, majority, snapshot) in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the read concern level to local in a MongoDB query.

MongoDB

db.collection.find().readConcern('[1]')

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

Alinearizable

Blocal

Csnapshot

Dmajority

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'majority' when you want the fastest local read.

Confusing 'snapshot' with 'local' read concern.

The local read concern returns the most recent data available on the node without waiting for replication.

2fill in blank

medium

Complete the code to set the read concern level to majority in a MongoDB query.

MongoDB

db.collection.find().readConcern('[1]')

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

Amajority

Blocal

Csnapshot

Davailable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'local' when you want guaranteed majority confirmation.

Using 'snapshot' which is different from majority.

The majority read concern ensures that the data read has been acknowledged by a majority of replica set members.

3fill in blank

hard

Fix the error in the code to use the snapshot read concern correctly.

MongoDB

db.collection.find().readConcern('[1]')

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

Alocal

Bmajority

Csnapshot

Dlinearizable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'majority' instead of 'snapshot' for transactions.

Using 'local' which does not guarantee snapshot isolation.

The snapshot read concern provides a point-in-time snapshot of the data for transactions and causal consistency.

4fill in blank

hard

Fill both blanks to set the read concern to majority and specify the read preference to primary.

MongoDB

db.collection.find().readConcern('[1]').readPreference('[2]')

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

Amajority

Blocal

Cprimary

Dsecondary

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing read preference with read concern values.

Using secondary read preference with majority read concern incorrectly.

Setting readConcern to majority ensures data is confirmed by most nodes. Setting readPreference to primary reads from the primary node.

5fill in blank

hard

Fill all three blanks to set a snapshot read concern, read from primary, and limit results to 5 documents.

MongoDB

db.collection.find().readConcern('[1]').readPreference('[2]').limit([3])

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

Alocal

Bprimary

C5

Dsnapshot

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'local' instead of 'snapshot' for consistent reads.

Forgetting to limit the number of documents.

This code sets the read concern to snapshot for consistent reads, reads from the primary node, and limits the output to 5 documents.