Creating field with multiple properties
If you want an array of strings maybe your should use a blob in you schema:

 'question_option' =&gt; [
          'type' =&gt; 'blob',
          'size' =&gt; 'big',
          'not null' =&gt; TRUE,
          'serialize' =&gt; TRUE
        ],


Note that by default 'size' = 'normal' which max storage value is 16KB so if it is enough for you use 'big'; 'big' can handle up to 4GB.
And for properties as follow:

$properties['question_options'] = MapDataDefinition::create()-&gt;setLabel(t('Options'))