Answer
MongoDB combines multiple indexes to satisfy a query when no compound index exists. This improves performance compared to full scans but is slower than a single optimal compound index.
Quick Answer
MongoDB can combine results from two separate indexes using index intersection (AND_HASH/AND_SORTED plan stages). The planner may choose this over a single compound index if it estimates fewer total keys examined. In practice, a well-designed compound index usually outperforms intersection due to lower overhead. Use explain() to verify - if intersection is being used consider adding a compound index instead.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ