MongoDB best schema design for efficiency

Question

So I'm fairly new to mongoDB but have used sql a fair bit. I'm hoping this is a fairly straightforward questions so I'll get stuck in.

Out of the following two schema designs, which is the most efficient / easiest to query? I'll be doing fairly straightforward queries (I hope). The "sales" objects will be much more complex than what I have outlined below. There will be approximately 30 shops in the database, expecting to grow to say 60 within a few years.

• option 1

    {
        name: "shop1",
        sales:
            [
                {
                    weekEnding: "5/1/2020",
                    sales: 156.50,
                    customers: 5
                },
                {
                    weekEnding: "12/1/2020",
                    sales: 256.50,
                    customers: 12
                },
            ]
    },
    {
        name: "shop2",
        sales:
            [
                {
                    weekEnding: "5/1/2020",
                    sales: 456.50,
                    customers: 9
                },
                {
                    weekEnding: "12/1/2020",
                    sales: 446.50,
                    customers: 19
                },
            ]
    },

• option 2

    {
        name: "shop1",
        weekEnding: "5/1/2020",
        sales: 156.50,
        customers: 5
    },
    {

        name: "shop1",
        weekEnding: "12/1/2020",
        sales: 256.50,
        customers: 12
    },

    {
        name: "shop2",
        weekEnding: "5/1/2020",
        sales: 456.50,
        customers: 9
    },
    {
        name: "shop2",
        weekEnding: "12/1/2020",
        sales: 446.50,
        customers: 19
    },

Answer 1

I'm not a MongoDB expert but I think you are much better off with option 2. With option 1 you have only about 30 documents in your database and all of them can grow quite large and I think MongoDB will have to rearrange them on disk when they change size since objects should be kept in a coherent memory space.

And I see no problem at all with option 2. It will work perfectly well to index the sales by shop and won't cause any performance issues.