MongoDB Interview Questions: Architecture Questions

Design a Replica Set

Create a configuration for a MongoDB replica set with three members and explain the role of each member.

Expected output: A replica set configuration with member roles described.

Hint: Include one primary and two secondary nodes.

Explain Sharding Components

Describe the function of shards, mongos, and config servers in a sharded MongoDB cluster.

Expected output: Clear explanation of each component's role.

Hint: Focus on data distribution and query routing.

A replica set is a group of mongod instances that maintain the same data set, providing redundancy and automatic failover. It ensures high availability by electing a primary node to handle writes and secondaries to replicate data.

Sharding distributes data across multiple servers called shards. Each shard holds a subset of the data. The mongos query router directs operations to the correct shard based on the shard key, enabling horizontal scaling.

Config servers store metadata and configuration settings for the sharded cluster. They help mongos route queries correctly and maintain cluster state.