db={"users":[{"_id":ObjectId("60360581ce8d63116c5ce6fb"),"userType":["STUDENT"],"firstName":"Shourv ","lastName":"Das"},{"_id":ObjectId("6027fdb087d0b94d18611db4"),"userType":["STUDENT"],"isVerified":false,"firstName":"Umor","lastName":"Ahmed"},{"_id":ObjectId("6027fd9587d0b94d18611db3"),"userType":["STUDENT"],"isVerified":false,"firstName":"Razel","lastName":"Khan"},{"_id":ObjectId("6027fd9587d0b94d18611db4"),"userType":["STUDENT"],"isVerified":false,"firstName":"Razel","lastName":"Khan"}],"sectionStudents":[{"_id":ObjectId("60d736baee3b6b154ccdcc33"),"course":ObjectId("5ffeec372b2234556439d1da"),"section":ObjectId("6002fae3e58bc750b4394229"),"student":ObjectId("60360581ce8d63116c5ce6fb"),},{"_id":ObjectId("60d63e44691df002f0e662ed"),"course":ObjectId("5ffeec372b2234556439d1da"),"section":ObjectId("6002fae3e58bc750b4394229"),"student":ObjectId("6027fdb087d0b94d18611db4"),},{"_id":ObjectId("60d63a9fddcd320314a16470"),"course":ObjectId("5ffeec372b2234556439d1da"),"section":ObjectId("6002fae3e58bc750b4394229"),"student":ObjectId("6027fd9587d0b94d18611db3"),}]}

db.users.aggregate([{$lookup:{from:"sectionStudents",let:{student:"$_id"},pipeline:[{$match:{$expr:{$eq:["$$student","$student"]},course:ObjectId("5ffeec372b2234556439d1da")}},{$limit:1}],as:"student"}},{$match:{student:[]}},{$unset:"student"}])