Sharding Overview

• What is "sharding"?

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  • Splitting a single collection among several MongoDB instances
  • In production, each shard should be a replica set

• Why would you use sharding?

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  • When a collection becomes too large for a single server

• What is a "sharded cluster"?

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  • A combination of the following:
  • MongoDB Shard Routing Service (mongos)
  • Configuration Server
  • Two or more shards

• How is key space allocated?

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  • Range based
  • Hash function based

• How should you choose a shard key?

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  • The key should be:
  • Relatively random, and
  • Provide for an even distribution of data