MongoDB MongoDB Replication and Sharding

Question 1

What is a replica set in MongoDB?

Accepted Answer

A group of mongod instances maintaining the same data set for redundancy

Answer

A set of identical database schema templates

Answer

A set of backup files taken at the same time

Answer

A collection of replicated index definitions

Question 2

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

Accepted Answer

Receives all write operations and records changes to the oplog

Answer

Stores the primary (most important) documents

Answer

Handles only read operations from the application

Answer

Acts as the configuration server for sharding

Question 3

How many votes are needed for a primary election in a MongoDB replica set?

Accepted Answer

A simple majority of all voting members

Answer

A unanimous vote from all members

Answer

At least two members must vote

Answer

The member with the highest priority wins automatically

Question 4

What is an arbiter in a MongoDB replica set?

Accepted Answer

A voting member that holds no data and only participates in elections

Answer

A member that arbitrates between conflicting writes

Answer

A read-only member for reporting purposes

Answer

A member that arbitrates between multiple primaries

Question 5

What is the oplog in MongoDB replication?

Accepted Answer

A capped collection that records all data-modifying operations on the primary

Answer

An operations performance log for monitoring

Answer

An optimizer log for query plans

Answer

An operational alert log for system events

Question 6

What write concern { w: 'majority' } ensures in MongoDB?

Accepted Answer

A majority of voting replica set members have acknowledged the write

Answer

Only the primary acknowledges the write

Answer

All replica set members have written the data to disk

Answer

The write is replicated to at least two members