@magnusbaeck
Is the syntax correct for the json though?
Can you access fields in this fashion after parsing to json (if in this case payload were the actual target)?
And to add to this, if the json structure is always the same, but some field names might change, can you do it with an index search?
For instance, in his example, if "order_id" were a dynamic name, but always at the same place, how could you access this field?