Replica set architecture mental model in MongoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a MongoDB replica set?

A MongoDB replica set is a group of mongod processes that maintain the same data set, providing redundancy and high availability.

beginner

What role does the primary node play in a replica set?

The primary node receives all write operations and replicates data to secondary nodes. It is the main point for data changes.

beginner

How do secondary nodes function in a replica set?

Secondary nodes replicate data from the primary node and can serve read operations if configured. They provide data redundancy.

intermediate

What happens during a primary node failure in a replica set?

The replica set automatically holds an election to select a new primary from the secondary nodes to maintain availability.

intermediate

Why is an arbiter used in a replica set?

An arbiter participates in elections to help choose a primary but does not store data, saving resources while maintaining voting balance.

What is the main responsibility of the primary node in a MongoDB replica set?

A Handle all write operations

B Store backup data only

C Serve read operations exclusively

D Participate in elections without storing data

The primary node handles all write operations and replicates data to secondary nodes.

What does a secondary node do in a replica set?

A Only votes in elections

B Handles all write operations

C Replicates data from the primary node

D Does not participate in the replica set

Secondary nodes replicate data from the primary to maintain redundancy.

What triggers an election in a MongoDB replica set?

A Manual user command only

B Secondary node failure

C Arbiter shutdown

D Primary node failure

An election is triggered automatically when the primary node fails to select a new primary.

What is the purpose of an arbiter in a replica set?

A Participate in elections without storing data

B Store data backups

C Serve read and write operations

D Replace the primary node

Arbiters help maintain voting balance during elections but do not store data.

Which of the following is NOT true about replica sets?

A They provide data redundancy

B They require manual intervention to elect a primary

C They allow automatic failover

D They consist of primary and secondary nodes

Replica sets automatically elect a primary without manual intervention.

Explain the roles of primary, secondary, and arbiter nodes in a MongoDB replica set.

Think about who writes data, who copies it, and who helps decide leadership.

Describe what happens in a replica set when the primary node fails.

Focus on the failover process and how the system stays online.