Answer
Compound indexes index multiple fields together, allowing MongoDB to speed up queries and sorting based on index prefix rules.
Quick Answer
Compound indexes cover multiple fields in a specific order. db.orders.createIndex({userId: 1, createdAt: -1}) supports queries filtering by userId and sorting by createdAt descending. This is much faster than two separate indexes because MongoDB traverses one B-tree. The order of fields in the index matters - place equality fields first, then sort fields, then range fields.
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SugharaIQ Editorial Team
Verified Answer
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Source: SugharaIQ