Mastering Table.Group in Power Query: Unlocking the fifth argument

Hello, Omid_Motamedise your 3rd usage of GroupKind.Local is so "unique" that I'd never recommend using it 😁 Have you ever tried it on lets say 5K rows of data? In Excel? Your code hits Source[Cost] list with List.Sum(List.Range(...)) so many times while you did not even bother with buffering it... Well, maybe I am wrong and PQ delegates this job to your source database (if it's your case) but I would prefer doing this with (pre-calculated) buffered list of running total cost.

let
    Source = Table1,
    cost = List.Buffer(Source[cost]), 
    rt_cost = List.Buffer(
        List.Generate(
            () => [i = 0, rt = cost{0}],
            (x) => x[i] < List.Count(cost),
            (x) => [i = x[i] + 1, rt = x[rt] + cost{i}],
            (x) => x[rt]
        )
    ),
    res = Table.Group(
        Source,
        "Index", 
        {"Count", each List.Sum([cost])},
        GroupKind.Local, 
        (s, c) => Number.From((rt_cost{c} - rt_cost{s}) >= 130)
    )
in
    res

 Meanwhile, you may skip column reference in 5th argument (x[Index] or y[Index] in your code) and use just "x" and "y" if you use just single column to group by ("Index") and skip curley braces {} in 2nd argument of Table.Group.