[{tester_id:"1",test_id:"1",score:40},{tester_id:"1",test_id:"2",score:50},{tester_id:"1",test_id:"3",score:70},{tester_id:"2",test_id:"1",score:50},{tester_id:"3",test_id:"2",score:20},{tester_id:"3",test_id:"3",score:60},{tester_id:"7",test_id:"5",score:40},{tester_id:"8",test_id:"4",score:50},{tester_id:"9",test_id:"4",score:70},]

db.collection.aggregate([{$match:{"tester_id":"1"}},{"$lookup":{"from":"collection","let":{"score":"$score","tester_id":"$tester_id"},"localField":"tester_id","foreignField":"test_id","pipeline":[{$match:{$expr:{"$and":[{$ne:["$tester_id","$$tester_id"]},{$gte:["$score","$$score"]}]}}},],"as":"result"}},{"$unwind":"$result"},{$group:{"_id":null,"result":{$push:"$result"}}},{"$replaceWith":{"$mergeObjects":"$result"}},{$project:{"_id":0}}])