Database
[{_id:ObjectId("654d5e00b560e4fd57bde48a"),identity:"9898"},{_id:ObjectId("654d5e0cb560e4fd57bde48b"),identity:"129898"},{_id:ObjectId("654d5e17b560e4fd57bde48c"),identity:"AABB9898"},{_id:ObjectId("654d5e17b560e4fd57bde48d"),identity:"AABB9898"},{_id:ObjectId("654d5e17b560e4fd57bde48e"),identity:"1234"},{_id:ObjectId("654d5e17b560e4fd57bde48f"),identity:"ABCD"}]
Query
db.collection.find({$expr:{$regexMatch:{input:"545454129898",regex:{$concat:["$identity",{$literal:"$"}]}}}})