We have data stored in mongodb by country code. Our document will look like the following,

```js
{
    "_id" : ObjectId("5d82009cddf8d111b0f5c0f9"),
    "title" : "Keystone Korner",
    "CA" : {
        "dlp" : 21.99,
        "dlpCurrencyCode" : "CAD",
        "sales" : {
            "changeProceedsPriorDay" : 0.0,
            "changeUnitsPriorDay" : 0,
            "consumerPriceCurrencyCode" : null,
            "last30Proceeds" : 0.0,
            "last30Units" : 0,
            "last365Proceeds" : 4.22,
            "last365Units" : 4,
            "last60Proceeds" : 0.0,
            "last60Units" : 0,
            "last7Proceeds" : 0.0,
            "last7Units" : 0,
            "last90Proceeds" : 0.0,
            "last90Units" : 0,
            "lastAvgSalesPrice" : 0.0,
            "lastAvgSalesPricePrior" : 0.0,
            "lastProceeds" : 0.0,
            "lastProceedsPct" : 0.0,
            "lastProceedsPrior" : 0.0,
            "lastSalesDate" : "2021-08-23",
            "lastUnits" : 0,
            "lastUnitsPct" : 0.0,
            "lastUnitsPrior" : 0
        }
    },
    "US" : {
        "dlp" : 17.99,
        "dlpCurrencyCode" : "USD",
        "sales" : {
            "changeProceedsPriorDay" : 0.0,
            "changeUnitsPriorDay" : 0,
            "consumerPriceCurrencyCode" : null,
            "last30Proceeds" : 4.18,
            "last30Units" : 2,
            "last365Proceeds" : 51.66,
            "last365Units" : 19,
            "last60Proceeds" : 4.18,
            "last60Units" : 2,
            "last7Proceeds" : 0.0,
            "last7Units" : 0,
            "last90Proceeds" : 7.37,
            "last90Units" : 4,
            "lastAvgSalesPrice" : 0.0,
            "lastAvgSalesPricePrior" : 0.0,
            "lastProceeds" : 0.0,
            "lastProceedsPct" : 0.0,
            "lastProceedsPrior" : 0.0,
            "lastSalesDate" : "2021-08-25",
            "lastUnits" : 0,
            "lastUnitsPct" : 0.0,
            "lastUnitsPrior" : 0
        }
    }
}

```

I have provided only few country listings here but each document can contain almost 80-100 different country listings.

Our requirement is to identify the most recent `lastSalesDate` from `sales` parent under each country. So if we are able to list all `lastSalesDate` we may be able to sort and limit it by 1

How do we achieve this without knowing parents (Country codes like US, CA, GB, etc..)?

Thanks in advance.