db={"users":[{"email":"test@mueller.com","firstName":"Gerd","lastName":"Müller","role":"Admin","isActive":true,"accountId":12345,"prices":[{"date":"2022-03-22T13:06:13.493+00:00","price":95},{"date":"2022-02-16T13:06:13.493+00:00","price":105}]},{"email":"tobias.noell@zeiss.com","firstName":"Tobias","lastName":"Noell","role":"SuperAdmin","isActive":true,"accountId":32661,}],"datasets":[{"eyeSize":54,"bridgeSize":15,"templeLength":135,"colorCode":"F010","colorDescription":"braun, rose gold","stateHistory":[{"state":"scanning","date":"2022-02-22T13:06:13.493+00:00",},{"state":"scanned","date":"2022-02-18T13:06:13.493+00:00",},{"state":"reconstructing","date":"2022-02-16T13:06:13.493+00:00",}]},{"eyeSize":54,"bridgeSize":15,"templeLength":135,"colorCode":"F011","colorDescription":"beige, silber","stateHistory":[{"state":"scanning","date":"2022-03-22T13:06:13.493+00:00",},{"state":"scanned","date":"2022-03-18T13:06:13.493+00:00",},{"state":"reconstructing","date":"2022-03-16T13:06:13.493+00:00",}]}]}

db.datasets.aggregate({"$lookup":{"from":"users","as":"details",let:{prices:"$prices"},pipeline:[{$match:{prices:{"$exists":true},$expr:{"$eq":["$stateHistory.date","$$prices.date"]}}},{"$group":{"_id":"$_id",cgPrice:{"$push":"$stateHistory.date"}}}]}})