(Quickly) Return date when goal value was achieved

Hello,

I have an Import SQL query containing manufacturing data for multiple locations.  I would like to be able to display when a location reached a specific goal (for example, return the date when Plant A hits 40 million cumulative units). I have a Measure that returns a date (see below), however it takes 3 minutes for the Dax query to complete.  Can anyone suggest a more efficient method?

My data is as below.

I have a Measure to return a Cumulative Total (seen above as [# Units - Cumulative]):

# Units - Cumulative = CALCULATE (
    SUM ( 'Query1'[Units] ),
    FILTER (
        ALL ( 'key_DateTable' ), 'key_DateTable'[Date] <= MAX ( 'key_DateTable'[Date] )
    )
)

I have used the following Measure, and it works, but it also takes ~3 minutes per goal and per manufacturing location.  That's simply too long to wait for the data.

# Milestone - 40 mill = MINX (
    DISTINCT ( Query1[PlantID] ),
    CALCULATE (
        VAR FirstDateOverTarget =
            FIRSTNONBLANK ( key_DateTable[Date], IF ( Query1[# Units - Cumulative] >= 40000000, 1 ) )
        RETURN
            FirstDateOverTarget
    )
)

Ideally, I would like to (quickly) be able to generate a table such as this one:

I would rather not create a Calculated Column (my understanding is that this will impact my performance), but I'm open to suggestions.  For what it's worth, I have roughly 80-100 different manufacturing locations and my daily data goes back to the mid 1990's.

Any feedback is greatly appreciated.  Thank you!