Read concern levels (local, majority, snapshot) in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the local read concern level in MongoDB guarantee?

The local read concern returns the most recent data on the node that processes the query, without waiting for replication to other nodes. It may include uncommitted or rolled-back data.

beginner

Explain the majority read concern level in MongoDB.

The majority read concern returns data that has been acknowledged by a majority of replica set members, ensuring the data is durable and won't be rolled back.

intermediate

What is the purpose of the snapshot read concern level?

The snapshot read concern provides a consistent view of data at a single point in time across the entire replica set, useful for transactions to read a stable dataset.

beginner

Which read concern level is best for reading the most up-to-date data without waiting for replication?

The local read concern is best for reading the most recent data on the node without waiting for replication.

intermediate

Why would you use majority read concern instead of local?

You use majority to ensure the data read is durable and acknowledged by most nodes, preventing reading data that might be rolled back, unlike local which may read uncommitted data.

Which read concern level returns data acknowledged by most replica set members?

A local

B linearizable

C snapshot

D majority

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

What does the snapshot read concern provide?

A A consistent view of data at a single point in time

B The most recent data on a single node

C Data that is not yet replicated

D Data only from the primary node

Snapshot read concern provides a consistent view of data at a single point in time across the replica set.

Which read concern level might return data that could be rolled back?

A local

B snapshot

C majority

D linearizable

Local read concern may return data that is not yet replicated and could be rolled back.

For a transaction requiring a stable dataset, which read concern is recommended?

A majority

B snapshot

C local

D available

Snapshot read concern is recommended for transactions to read a stable, consistent dataset.

Which read concern level does NOT wait for replication to other nodes?

A majority

B linearizable

C local

D snapshot

Local read concern returns data immediately from the node without waiting for replication.

Describe the differences between local, majority, and snapshot read concern levels in MongoDB.

Think about data freshness, durability, and consistency.

When would you choose majority read concern over local in a MongoDB application?

Consider the risk of reading uncommitted or unstable data.