What are indexes in MongoDB? | MongoDB Interview Questions

What You'll Learn

Indexes improve query performance by allowing MongoDB to find documents without scanning every document in a collection.

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db.users.createIndex({ email: 1 });  // Ascending
db.users.createIndex({ age: -1 });   // Descending

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db.users.createIndex({ lastName: 1, firstName: 1 });

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db.users.createIndex({ email: 1 }, { unique: true });

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db.articles.createIndex({ content: "text" });
db.articles.find({ $text: { $search: "mongodb tutorial" } });

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db.sessions.createIndex({ createdAt: 1 }, { expireAfterSeconds: 3600 });

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// List all indexes
db.users.getIndexes();

// Drop index
db.users.dropIndex("email_1");

// Drop all indexes (except _id)
db.users.dropIndexes();

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db.users.find({ email: "john@example.com" }).explain("executionStats");
// Check "totalDocsExamined" vs "nReturned"