Yes, if this is a crucial requirement and you need to do this often, and the benefits outway the downside of writes being slowed down by this index.
No if this is something you don't use too often and the benefits are small compared to the hit in writes that will be incurred, or if you can achieve the same result without using an index.
In any case, experiment and see if things work better - if they don't then remove the index.
Justin Njoh
MVPs & POCs on NoSQL DBs - why not ?
Yes and no.
Yes, if this is a crucial requirement and you need to do this often, and the benefits outway the downside of writes being slowed down by this index.
No if this is something you don't use too often and the benefits are small compared to the hit in writes that will be incurred, or if you can achieve the same result without using an index.
In any case, experiment and see if things work better - if they don't then remove the index.