Read from secondaries trade-offs in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read from secondary nodes in MongoDB.

MongoDB

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

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

Aprimary

BprimaryPreferred

Csecondary

Dnearest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'primary' instead of 'secondary' will read only from the primary node.

Using 'nearest' may read from primary or secondary, not guaranteed secondary only.

Using secondary as the read preference directs reads to secondary nodes.

2fill in blank

medium

Complete the code to set read preference to secondary with a tag in MongoDB.

MongoDB

db.collection.find().readPref('[1]', [{ region: 'us-east' }])

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

Asecondary

Bprimary

CsecondaryPreferred

Dnearest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'primary' ignores secondary nodes.

Using 'nearest' may read from any node, not guaranteed secondary.

Setting read preference to secondary with tags reads from secondaries matching the tag.

3fill in blank

hard

Fix the error in the read preference setting to read from secondaries.

MongoDB

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

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

Asecondary

Bprimary

CprimaryPreferred

DsecondaryPreferred

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'secondaryPreferred' allows reading from primary if no secondary is available.

Using 'primary' reads only from the primary node.

The correct read preference to read only from secondaries is secondary.

4fill in blank

hard

Fill both blanks to read from secondaries with a max staleness of 90 seconds.

MongoDB

db.collection.find().readPref('[1]', [], { maxStalenessSeconds: [2] })

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

Asecondary

Bprimary

C90

D60

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'primary' ignores secondaries.

Setting maxStalenessSeconds too low or too high can cause errors or stale data.

Setting read preference to secondary with maxStalenessSeconds limits how stale the data can be.

5fill in blank

hard

Fill all three blanks to read from secondaries with tag 'dc:west' and max staleness 120 seconds.

MongoDB

db.collection.find().readPref('[1]', [[2]], { maxStalenessSeconds: [3] })

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

Asecondary

B{ dc: 'west' }

C120

Dprimary

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'primary' instead of 'secondary' ignores secondaries.

Incorrect tag format causes no matching nodes.

Omitting maxStalenessSeconds allows unlimited staleness.

This sets the read preference to secondary, filters secondaries by the tag dc:west, and limits staleness to 120 seconds.