[{"field1":"","field2":1,"createdAccounts":{"test@gmail.com":{"id":["a","b","c"]}}},{"field1":"","field2":2,"createdAccounts":{"test1@gmail.com":{"id":["a","b","c"]},"test2@gmail.com":{"id":["a","b","c"]}}},{"field1":"","field2":3,"createdAccounts":{"test3@gmail.com":{"id":["a","b","c"]}}}]

db.collection.aggregate([{"$addFields":{"email":{"$getField":{"field":"test2@gmail.com","input":"$createdAccounts"}}}},{"$match":{"email":{"$exists":true}}},{"$project":{"email":0}}])