In Workgen, there is a function called kv_compute_max that derives the maximum size a key/value can be.

_key._size and _value._size are int and they are assigned to internal->_keysize and internal->_valuesize which are of type uint_t.

The max size is computed this way:

    uint64_t max;
    if (size > 1)
        max = power64(10, (size - 1)) - 1;
    else
        max = 0;

And then it is assigned to internal->_keymax and internal->_valuemax which are of type uint_t.

Everything could be changed to uint64_t.