[{"collection":"collection","count":10,"content":{"createdAt":{"type":"date","startDate":"2024-08-01T00:00:00Z","endDate":"2024-10-31T00:00:00Z"}}}]

db.collection.aggregate([{"$match":{"$expr":{"$let":{"vars":{/** your input here*/"yearInput":2024,"monthInput":10},"in":{"$and":[{"$eq":["$$yearInput",{"$year":"$createdAt"}]},{"$eq":["$$monthInput",{"$month":"$createdAt"}]}]}}}}},{"$count":"count"}])