MongoDB Replication and Sharding Flashcards

What is horizontal scaling in MongoDB achieved through?

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.

What is a shard key in MongoDB sharding?

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.

What is a mongos in a MongoDB sharded cluster?

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).

What stores cluster metadata in a MongoDB sharded cluster?

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.

What is a chunk in MongoDB sharding?

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.

What is a targeted query in a sharded MongoDB cluster?

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.