What happens during an index scan operation?

During an index scan operation, the database engine utilizes the index to efficiently locate documents that match a specific query condition. Instead of scanning through all the documents in the collection, which would be time-consuming, the index allows the system to quickly navigate to the relevant entries.

When an index scan occurs, it checks each index entry to determine whether it satisfies the condition specified in the query. This process uses the structure of the index, which is typically sorted, to quickly identify all relevant keys. After finding the matching index entries, the database can efficiently retrieve the associated documents based on those keys.

This is an important mechanism for optimizing query performance, as it significantly reduces the workload and time taken compared to a full collection scan. Therefore, this answer accurately describes the core operation of how an index scan functions within MongoDB and similar database systems.