It should but requires testing

%xsd.base64Binary is essentially a string so you can't write more than 3,5 mb there.

Change property definition to %Stream.GlobalCharacter instead.

Global buffers are one of the keys to performance.   

Yes, that's why if streams are to be stored in the db they should be stored in a separate db with distinct block size and separate global buffers.

Some time ago I was working on the issue of a fast data generation for an arbitrary data model.

Data model was connected (object properties) and so to generation was going in stages from low-cardinality independent tables (i.e. product) to high-cardinality dependent tables (i.e. orders). Furthermore tables did not have continuous IDs, there were gaps (due to sharding in my case but even if there's no hard delete we might want to exclude soft deleted rows).

Here's the approach I used.

1. For a given class build a local with all ranges of IDs:

/// d ##class().Ranges()
ClassMethod Ranges(class As %Dictionary.Classname, Output ranges)
{
    kill ranges    

    set table = ##class(%CSP.UI.Portal.SQL.Home).Quoter2(##class(%DeepSee.Utils).%GetSQLTableName(class))
    
    set rs = ##class(%SQL.Statement).%ExecDirect(,"SELECT ID FROM " _ table _ " ORDER BY ID ASC")

    do rs.%Next()
    set start = rs.ID
    set end = rs.ID
    while rs.%Next() {
        if rs.ID - 1 = end {
            d $i(end)
        } else {
            set ranges($i(ranges)) = $lb(start, end-start)
            set start = rs.ID
            set end = rs.ID
        }
    }
    
    set ranges($i(ranges)) = $lb(start, end-start)
}

This method accepts class name and returns this structure:

ranges(num) = $lb(startID, length)

2. Call GetRandomInRanges method to get random ID from ranges local:

/// d ##class().GetRandomInRanges()
ClassMethod GetRandomInRanges(ByRef ranges)
{
    set sum = 0
    
    for i=1:1:ranges {
        set sum = sum + $lg(ranges(i),2)
    }
    
    set threshold = $random(sum) + 1
    
    set sum = 0
    for chunk=1:1:ranges {
        set sum = sum + $lg(ranges(chunk),2)
        quit:sum>=threshold
    }    
    
    set val = ranges(chunk)
    if $listvalid(val) {
        if $ll(val)=2 {
            set val = $lg(val, 1) + $random($lg(val, 2))
        } else {
            set:$listvalid(val) val = $lg(val, ($random($ll(val))+1))
        }
    }
    
    quit val
}

This method guarantees that returned IDs would conform to the normal distribution.

Ranges should be called once and GetRandomInRanges  can be called as often as needed.

Maybe you can go into Application Roles tab and add %ALL role.

After that try again from private window or another browser.

Unknown User must also be enabled.

This is only for dev/testing.

Do you want to send a custom header with your HTTP request?

cacheusr is a linux user.