Database

db={"reviews":[{"_id":ObjectId("5e4be86809d2675c3cdf8387"),"reviewDate":ISODate("2020-02-18T15:51:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be85d09d2675c3cdf8386"),"score":5},{"_id":ObjectId("5e4be85709d2675c3cdf8385"),"reviewDate":ISODate("2020-02-18T11:21:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be85009d2675c3cdf8384"),"score":1},{"_id":ObjectId("5e4be84b09d2675c3cdf8383"),"reviewDate":ISODate("2020-02-18T17:08:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be84109d2675c3cdf8382"),"score":3},{"_id":ObjectId("5e4be83b09d2675c3cdf8381"),"reviewDate":ISODate("2020-02-18T19:15:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be83009d2675c3cdf8380"),"score":2,},{"_id":ObjectId("5e4be82a09d2675c3cdf837f"),"reviewDate":ISODate("2020-02-18T14:48:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be82309d2675c3cdf837e"),"score":4},{"_id":ObjectId("5e4be81e09d2675c3cdf837d"),"reviewDate":ISODate("2020-02-18T15:58:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be81309d2675c3cdf837c"),"score":4},{"_id":ObjectId("5e4be80e09d2675c3cdf837b"),"reviewDate":ISODate("2020-02-18T02:55:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be80409d2675c3cdf837a"),"score":4},{"_id":ObjectId("5e4be0b709d2675c3cdf8379"),"reviewDate":ISODate("2020-02-18T07:11:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be0af09d2675c3cdf8378"),"score":5},{"_id":ObjectId("5e4be0a909d2675c3cdf8377"),"reviewDate":ISODate("2020-02-18T11:18:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be09c09d2675c3cdf8376"),"score":1},{"_id":ObjectId("5e4be09709d2675c3cdf8375"),"reviewDate":ISODate("2020-02-18T18:02:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4be08b09d2675c3cdf8374"),"score":4},{"_id":ObjectId("5e4be07a09d2675c3cdf8373"),"reviewDate":ISODate("2020-02-18T12:21:22.584+03:00"),"product":ObjectId("5e4bdffb09d2675c3cdf8371"),"user":ObjectId("5e4bdfa809d2675c3cdf8370"),"score":3}],"products":[{"_id":ObjectId("5e4be00709d2675c3cdf8372"),"name":"Product2","price":2},{"_id":ObjectId("5e4bdffb09d2675c3cdf8371"),"name":"Product1","price":1}],"users":[{"_id":ObjectId("5e4be85d09d2675c3cdf8386"),"username":"User11"},{"_id":ObjectId("5e4be85009d2675c3cdf8384"),"username":"User10"},{"_id":ObjectId("5e4be84109d2675c3cdf8382"),"username":"User9"},{"_id":ObjectId("5e4be83009d2675c3cdf8380"),"username":"User8"},{"_id":ObjectId("5e4be82309d2675c3cdf837e"),"username":"User7"},{"_id":ObjectId("5e4be81309d2675c3cdf837c"),"username":"User6"},{"_id":ObjectId("5e4be80409d2675c3cdf837a"),"username":"User5"},{"_id":ObjectId("5e4be0af09d2675c3cdf8378"),"username":"User4"},{"_id":ObjectId("5e4be09c09d2675c3cdf8376"),"username":"User3"},{"_id":ObjectId("5e4be08b09d2675c3cdf8374"),"username":"User2"},{"_id":ObjectId("5e4bdfa809d2675c3cdf8370"),"username":"User1"}]}

Query

db.products.aggregate([{$match:{_id:ObjectId("5e4bdffb09d2675c3cdf8371")}},{$lookup:{from:"reviews",localField:"_id",foreignField:"product",as:"reviews"}},{$unwind:"$reviews"},{$sort:{"reviews.reviewDate":-1}},{$lookup:{from:"users",localField:"reviews.user",foreignField:"_id",as:"user"}},{$addFields:{"reviews.user":{$arrayElemAt:["$user",0]}}},{$project:{user:0}},{$group:{_id:"$_id",reviews:{"$push":"$reviews"},"doc":{"$first":"$$ROOT"}}},{$replaceRoot:{newRoot:{$mergeObjects:["$doc",{"reviews":"$reviews"}]}}}])

Result