MongoDB MongoDB Replication and Sharding 2 — Questions and Answers
Question 1: What is horizontal scaling in MongoDB achieved through?
- Adding more CPU and RAM to existing servers
- Sharding data across multiple servers (Correct answer)
- Adding more replica set members
- Using faster NVMe storage
Correct answer: Sharding data across multiple servers
Sharding distributes data across multiple machines (shards), allowing MongoDB to handle datasets and throughput that exceed single-server capacity.
Question 2: What is a shard key in MongoDB sharding?
- An encryption key for shard data
- The field(s) used to partition documents across shards (Correct answer)
- A unique identifier for each shard server
- A key that unlocks a shard for maintenance
Correct answer: The field(s) used to partition documents across shards
The shard key determines how documents are distributed across shards; choosing a good shard key is critical for even data distribution and query efficiency.
Question 3: What is a mongos in a MongoDB sharded cluster?
- A monitoring service for shard health
- A query router that directs client requests to the appropriate shard(s) (Correct answer)
- The primary shard for system collections
- A shard configuration backup service
Correct answer: A query router that directs client requests to the appropriate shard(s)
mongos is a routing service that acts as an interface between the client and the sharded cluster, directing queries and writes to the correct shard(s).
Question 4: What stores cluster metadata in a MongoDB sharded cluster?
- The primary shard
- mongos instances
- Config servers (a separate replica set) (Correct answer)
- The admin database on each shard
Correct answer: Config servers (a separate replica set)
Config servers form a dedicated replica set that stores the cluster's metadata, including chunk ranges and shard locations.
Question 5: What is a chunk in MongoDB sharding?
- A 64MB block of data on disk
- A contiguous range of shard key values that MongoDB migrates as a unit (Correct answer)
- A batch of documents processed together
- A compressed segment of collection data
Correct answer: A contiguous range of shard key values that MongoDB migrates as a unit
Chunks are contiguous ranges of shard key values; MongoDB automatically splits and migrates chunks to balance data across shards.
Question 6: What is a targeted query in a sharded MongoDB cluster?
- A query with specific performance targets set
- A query that includes the shard key, allowing mongos to route it to specific shard(s) (Correct answer)
- A query using targeted indexes only
- A query from an authorized administrative account
Correct answer: A query that includes the shard key, allowing mongos to route it to specific shard(s)
A targeted query includes the shard key in its filter, enabling mongos to route it to only the relevant shard(s) rather than broadcasting to all shards.
MongoDB MongoDB Replication and Sharding 2
What is horizontal scaling in MongoDB achieved through?