Example: email storage

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Shard Key Considerations

Example: email storage


{
    _id: ObjectId("51156a11056d6f966f268f7f"),
    user: 37113,
    time: ISODate( '2013-04-24 10:38:05 '),
    subject: "This is a test",
    recipients: [ "derick@10gen.com", "derick@example.com" ],
    body: "..."
}


• Lots of emails per user
• Most common query: get user emails sorted by time
• Index on { _id: 1 }, { user: 1, time: -1 },