In addition to the numerous index types MongoDB supports, indexes can also have various properties. The following documents detail the index properties that you can select when building an index.
- TTL Indexes
- The TTL index is used for TTL collections, which expire data after a period of time.
- Unique Indexes
- A unique index causes MongoDB to reject all documents that contain a duplicate value for the indexed field.
- Sparse Indexes
- A sparse index does not index documents that do not have the indexed field.