Database
[{"_id":ObjectId("639789e84500571417934300"),"72uebaa27279b22p348e61870a6a8840something":[{"price":130,"date":1670874476},{"price":107,"date":1672258500}]},{"_id":ObjectId("639789e84500571417934301"),"72uebaa27279b22p348e61870a6a8840otherthing":[{"price":130,"date":1670874476},{"price":107,"date":1672258500}]}]
Query
db.collection.aggregate([{$addFields:{arraydoc:{$objectToArray:"$$ROOT"}}},{$match:{"arraydoc.k":{$regex:"something"}}},{$project:{arraydoc:0}}])