I have a RESTlet, where I start with an invoiceID and find the sales order, then find the item fulfillment and then find the items. But can I go the other way. From an itemID, can I find the sales order? Do I have to use search in that case?

doesnt really sound sane

The items have a unique id

if you are doing a search on the item fulfillment, then you want to use the inventory detail join

@battk I am struggling with the search API. Do you think it could be possible to use records ? Something like:

const objRecord = record.load({
        type: record.Type.INVENTORY_NUMBER,
        id: 'bcy32scy',
    });

Would require internal id

No, I can't search for it in the UI. But I find it when I do this:

search.create({
    type: 'inventorynumber',
    filters: ['inventorynumber', 'is', 'bcy32scy'],
    columns: ['inventorynumber']
  }).run()
    .each(function(result) {
      log.debug(result.id);
      return true;
    });

if you are searching by the number of the item number, then you probably want to use the item number join instead

@battk I must be miss-understanding this completely. I just want to find the item-fulfillment or sales-order that contains the item with serial-number: bcy32scy.

First step to a solution should be making the search that does what you want in the ui