Index Types and Strategies

Common Index Types

Beyond single-field indexes, MongoDB supports several specialised index types suited to different query patterns.

• Single-field — index on one field ({ age: 1 })
• Compound — index on multiple fields; field order and sort direction matter
• Multikey — automatically created when the indexed field is an array
• Text — enables full-text search with $text and $search
• TTL (Time-To-Live) — automatically expires documents after a set duration (great for sessions/logs)

// Text index for searching student bios
db.students.createIndex({ bio: "text" });
db.students.find({ $text: { $search: "react developer" } });

// TTL index: delete documents 30 days after createdAt
db.sessions.createIndex({ createdAt: 1 }, { expireAfterSeconds: 2592000 });