[{"studentid":"stu-1234","dept":"geog","teacher_id":1,"LastSwipeTimestamp":"2021-11-25T10:50:00.5230694Z"},{"studentid":"stu-1234","dept":"geog","teacher_id":2,"LastSwipeTimestamp":"2021-11-25T11:50:00.5230694Z"},{"studentid":"stu-abc","dept":"geog","teacher_id":11,"LastSwipeTimestamp":"2021-11-25T09:15:00.5230694Z"},{"studentid":"stu-abc","dept":"geog","teacher_id":21,"LastSwipeTimestamp":"2021-11-25T11:30:00.5230694Z"}]

db.collection.aggregate([{$match:{"studentid":{"$in":["stu-abc","stu-1234"]},"dept":"geog"}},{$sort:{"LastSwipeTimestamp":-1}},{$group:{"_id":{"studentid":"$studentid","dept":"$dept"},"teacher_id":{$first:"$teacher_id"},"LastSwipeTimestamp":{$first:"$LastSwipeTimestamp"}}},{$project:{_id:0,"studentid":"$_id.studentid","dept":"$_id.dept","teacher_id":"$teacher_id","LastSwipeTimestamp":"$LastSwipeTimestamp"}}])