db={"users":[{"_id":"6gfg85983266db5fdgs578","email":"xyz@gmail.com","role":"user","systemIDs":["12345678","87654321"],"createdAt":"2022-02-13T16:31:34.119+0000","updatedAt":"2022-02-13T16:31:34.119+0000","__v":0},{"_id":"6gfg85993266db5fdgs578","email":"abc@gmail.com","role":"user","systemIDs":["1111111","2135684"],"createdAt":"2022-02-13T16:31:34.119+0000","updatedAt":"2022-02-13T16:31:34.119+0000","__v":0}],"systems":[{"_id":"62093fdsfsdfs97e1","systemID":"12345678","err":[1,5,10],"__v":0},{"_id":"62094fdsfsdfs97e1","systemID":"87654321","err":[3,7],"__v":0},{"_id":"62087dsfsdfs97e1","systemID":"11111111","err":[],"__v":0},]}

db.users.aggregate([{"$match":{"email":"xyz@gmail.com"}},{"$lookup":{"from":"systems","localField":"systemIDs","foreignField":"systemID","as":"systemIDs"}}])