Causal consistency concept in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable causal consistency in a MongoDB session.

MongoDB

const session = client.startSession({ causalConsistency: [1] });

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

Afalse

Btrue

Cnull

Dundefined

Attempts:

3 left

💡 Hint

Common Mistakes

Using false disables causal consistency.

Passing null or undefined does not enable causal consistency.

Setting causalConsistency to true enables causal consistency for the session.

2fill in blank

medium

Complete the code to start a transaction with causal consistency in MongoDB.

MongoDB

session.startTransaction({ readConcern: { level: [1] } });

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

A"available"

B"local"

C"linearizable"

D"majority"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "local" does not guarantee causal consistency.

Using "linearizable" is stricter but not required here.

Using "majority" read concern ensures causal consistency in transactions.

3fill in blank

hard

Fix the error in the code to maintain causal consistency when reading after a write.

MongoDB

await collection.insertOne({ name: "Alice" }, { session: [1] });
const doc = await collection.findOne({ name: "Alice" }, { session: [1] });

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

Aundefined

Bnull

Csession

Dclient

Attempts:

3 left

💡 Hint

Common Mistakes

Not passing the session to the read operation.

Using different session objects for write and read.

Passing the same session object to both operations ensures causal consistency.

4fill in blank

hard

Fill both blanks to create a session with causal consistency and start a transaction with the correct read concern.

MongoDB

const session = client.startSession({ causalConsistency: [1] });
session.startTransaction({ readConcern: { level: [2] } });

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

Atrue

Bfalse

C"majority"

D"local"

Attempts:

3 left

💡 Hint

Common Mistakes

Setting causalConsistency to false disables causal consistency.

Using "local" read concern does not guarantee causal consistency.

Enable causal consistency with true and use "majority" read concern for transactions.

5fill in blank

hard

Fill all three blanks to read a document with causal consistency after a write in the same session.

MongoDB

const session = client.startSession({ causalConsistency: [1] });
await collection.insertOne({ item: "book" }, { session: [2] });
const result = await collection.findOne({ item: "book" }, { session: [3] });

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

Atrue

Bsession

Cfalse

Dclient

Attempts:

3 left

💡 Hint

Common Mistakes

Not enabling causal consistency in the session.

Using different session objects or none at all.

Enable causal consistency with true and use the same session object for both write and read operations.