I have a large mongo collection, when I run {"$and":[{"fieldCheck":"1"},{"timestamp":{"$lt": MAX_SAFE_INTEGER}}]}, the query results the output fast, but when i sort by {timestamp: -1, _id: -1} with the previous filters then the query takes forever.

The collection is indexed with composite index {timestamp: 1, _id: 1}, also fieldCheck is indexed with _id {fieldCheck: 1, _id: 1}

Whats wrong is going on?

I tried indexing mentioned.