How do indexes enhance query performance in MongoDB?

Indexes in MongoDB significantly enhance query performance by allowing the database to quickly locate and retrieve documents. When a query is executed, if an index has been created on the fields specified in the query, MongoDB can use this index to find the relevant documents without having to perform a full collection scan. This means that instead of checking every document in the collection, MongoDB only accesses the necessary documents identified through the index.

Using an index reduces the amount of data that needs to be processed, which leads to faster query performance and more efficient use of resources. This is especially important for large collections, where full scans would be time-consuming and resource-intensive.

The use of indexes optimizes the decision-making process for querying, improves response times, and ultimately results in a more efficient database operation.