MongoDB $lookup inside nested array performance & best practice issue

Question

In MongoDB I have:

Collection customers with embedded array orders:

db.customers.insert([
{_id: 1, name: "John", orders: [
  {articleId: 1, quantity: 10},
  {articleId: 2, quantity: 5}
]}]);

Collection articles

db.articles.insert([
{_id: 1, name: "computer"},
{_id: 2, name: "bike"}
]);

This question is not about design. I investigated a lot into the design, so that is fixed for this question. The collections customers, orders, articles is not my real case. I just took it as an example.

I want this result:

{_id: 1, name: "John", orders: [
  {articleId: 1, name: "computer", quantity: 10},
  {articleId: 2, name: "bike", quantity: 5}
]}

I can get this result with the following query:

db.customers.aggregate([
  { $match: { "_id": 1 } },
  { $unwind: "$orders" },
  {
    $lookup: {
      from: "articles",
      localField: "orders.articleId",
      foreignField: "_id",
      as: "article"
    }
  },
  { $unwind: "$article" },
  { $addFields: { "orders.name": "$article.name" } },
  { $project: { article: 0 } },
  {
    $group: {
      _id: "$_id",
      name: { "$first": "$name" },
      orders: { "$push": "$orders" }
    }
  }
]);

Is this the best possible query?

There are much more properties for every collection. And in case of a collection of 20 million customers. customers have an average of 50 orders per customer. And let say there are 80 articles. Also this query is running every minute. So I need to use as less resources as possible.

Or is there a smarter query that has a better performance using less resources?