Power Query: Filter to Latest Date Row

Hi HenryJS ，

Base data:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjazNFDSUXLNLcjJr0wtUvDJTEzKzMksqVTwzCsuLUrMS04FShsZGBnpm+obGivF6gD1WBpZAgUDivLTUouLM/PzEnOAqlNSc/Nw6DNH1obXBuJUGkJUxgIA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [externalid = _t, doctype = _t, Expiry = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"externalid", Int64.Type}, {"doctype", type text}, {"Expiry", type date}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"externalid"}, {{"allrows",each Table.AddIndexColumn(
        Table.Sort(_,{{"Expiry", 
        Order.Ascending}}), "Row Rank",1,1),  each _, type table [externalid=nullable number, doctype=nullable text, Expiry=nullable date]}}),
    #"Expanded allrows" = Table.ExpandTableColumn(#"Grouped Rows", "allrows", {"externalid", "doctype", "Expiry", "Row Rank"}, {"allrows.externalid", "allrows.doctype", "allrows.Expiry", "allrows.Row Rank"}),
    #"Filtered Rows" = Table.SelectRows(#"Expanded allrows", each ([allrows.Row Rank] = 1))
in
    #"Filtered Rows"

Final output:

refer:

https://data-witches.com/2020/10/21/adding-a-row-rank-based-on-a-different-column-with-power-query/ 

Best Regards
Lucien