[{"id":"0001","date":ISODate("2021-01-01T00:00:00Z"),"price":"50"},{"id":"0001","date":ISODate("2021-01-02T00:00:00Z"),"price":"40"},{"id":"0001","date":ISODate("2021-01-03T00:00:00Z"),"price":"30"},{"id":"0001","date":ISODate("2021-01-04T00:00:00Z"),"price":"10"},{"id":"0001","date":ISODate("2021-01-05T00:00:00Z"),"price":"20"},{"id":"0002","date":ISODate("2021-01-01T00:00:00Z"),"price":"100"},{"id":"0002","date":ISODate("2021-01-02T00:00:00Z"),"price":"110"},{"id":"0002","date":ISODate("2021-01-03T00:00:00Z"),"price":"120"},{"id":"0002","date":ISODate("2021-01-04T00:00:00Z"),"price":"130"},{"id":"0002","date":ISODate("2021-01-05T00:00:00Z"),"price":"140"}]

db.collection.aggregate([{"$sort":{"date":-1}},{"$group":{"_id":"$id","g":{"$push":{"price":"$price","date":"$date"}},"latest-date":{"$max":"$date"},"price":{"$first":"$price"}}},{"$addFields":{"days-date-found":{"$reduce":{"input":"$g","initialValue":[-1,-1,false],"in":{"$let":{"vars":{"days_date_found":"$$value","m":"$$this"},"in":{"$let":{"vars":{"days":{"$arrayElemAt":["$$days_date_found",0]},"date":{"$arrayElemAt":["$$days_date_found",1]},"found":{"$arrayElemAt":["$$days_date_found",2]}},"in":{"$switch":{"branches":[{"case":"$$found","then":"$$days_date_found"},{"case":{"$gt":["$$m.price","$price"]},"then":["$$days","$$m.date",true]}],"default":[{"$add":["$$days",1]},"$$m.date",false]}}}}}}}}}},{"$addFields":{"days":{"$arrayElemAt":["$days-date-found",0]},"closest-date":{"$cond":[{"$arrayElemAt":["$days-date-found",2]},{"$arrayElemAt":["$days-date-found",1]},"$latest-date"]}}},{"$unset":["days-date-found","g"]}])