Database
[{linkedAccount:[{accountId:"639f131640e86ede985400aa",comments:[]},{accountId:"639f131qwqwqe86ede985400aa",comments:[]},{accountId:"639f131640e86ede985400aa",comments:[]}]}]
Query
db.collection.find({"linkedAccount.accountId":"639f131640e86ede985400aa"},{"linkedAccount.$":1})