What type of queries can compound indexes support?

Compound indexes in MongoDB are designed to support queries that match on the prefix of the index fields. This means that if you create a compound index on multiple fields, queries can efficiently utilize this index even when they specify only the leading fields of the index.

For example, if you have a compound index on fields "firstName" and "lastName," a query that filters on "firstName" will be able to take advantage of this index. Additionally, queries that filter on both "firstName" and "lastName" will also be supported. However, a query that only uses "lastName" will not benefit from the compound index, as the leading field is not specified.

This prefix matching is crucial because it allows MongoDB to conduct efficient range-based lookups or exact matches based on the initial fields of the compound index, optimizing query performance.