MongoDB Administrator's Guide

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Over time, you may come across scenarios that require redesigning your indexing strategy. This may be by adding a new feature in your application or simply by identifying a more appropriate key that can be indexed. In either case, it is highly advisable to remove older (unused) indexes to ensure you do not have any unnecessary overhead on the database.

In order to remove an index, you can use the db.<collection>.dropIndex(<index_name>). If you are not sure about your index name, use the db.<collection>.getIndexes() function.