[{"_id":{"$oid":"634a9d1b269c99e9364e8750"},"marks":[{"results":[{"product":"Abc","score":55}]}]},{"_id":{"$oid":"634a9fae269c99e9364e8755"},"marks":[{"results":[{"product":"Abc","score":10},{"product":"Xyz","score":5}]}]},{"_id":{"$oid":"634a9fae269c99e9364e8756"},"marks":[{"results":[{"product":"Abc","score":8},{"product":"Xyz","score":7}]}]},{"_id":{"$oid":"634a9fae269c99e9364e8757"},"marks":[{"results":[{"product":"Abc","score":7},{"product":"Xyz","score":8}]}]}]

db.collection.aggregate([{$match:{"marks.results.product":"Xyz"}},{$limit:1},{$unwind:"$marks"},{$unwind:"$marks.results"},{$match:{"marks.results.product":"Xyz"}}])