midMongoDB
What is a Partial Index?
Updated May 1, 2026
Short answer
Partial indexes only index documents that meet a specified filter expression.
Deep explanation
This reduces index size and storage requirements while still providing performance benefits for specific subsets of data.
Real-world example
Indexing only active users to save space in a massive database.
Common mistakes
- Querying for documents that don't meet the filter and expecting index speed.
Follow-up questions
- Difference between Partial and Sparse indexes?