So the method queried the parents at one go first and then collected all the child IDs into an array and then make batched calls to find those child records. Tried changing the find logic the other way around, search for children by using `parent: <PARENT_ID>` for all parents. That is faster

Okay maybe I'm overthinking here, why not just use an aggregation query that hydrates child records by using $lookup? That turned out to be faster as the calls to mongodb were few Also, updated the $projection clause to select only the required fields. Result: 200 hydrated parents in 2s!!!