db={"sales":[{"_id":1,"property":ObjectId("65b536f31372826ba8433cc0"),"name":"Hat"},{"_id":2,"property":ObjectId("65b536f31372826ba8433cc1"),"name":"Shoes"},{"_id":3,"property":ObjectId("65b536f31372826ba8433cc2"),"name":"Scarf"}],"properties":[{"_id":ObjectId("65b536f31372826ba8433cc0"),"size":"L","propInfo":{"propName":"Red","material":"Wool"}},{"_id":ObjectId("65b536f31372826ba8433cc1"),"size":"M","propInfo":{"propName":"Blue","material":"Leather"}},{"_id":ObjectId("65b536f31372826ba8433cc2"),"size":"S","propInfo":{"propName":"Green","material":"Poly"}}]}

db.sales.aggregate([{$lookup:{from:"properties",localField:"property",foreignField:"_id",as:"property"}},{$unwind:"$property"},{$match:{"property.propInfo.propName":"Blue"}},{$project:{"name":1,"property.propInfo.propName":1,"size":1}}])