REST API - Reduce number of POSTS operations - api

Question

I have designed some API which have some nested resources and I am wondering how to reduce the number of POSTS when I am creating some records.
for example, I have the following resources:
/orders/
and
/orders/{order_id}/products/
at the moment I need to run two POST separately if I need to create a new order or a new order's product but I would like to reduce the time for this and run only one POST.
Is this possible? is there any documentation I can read about this?
Thank you

Answer 1

Although you might have found your answer in an other thread there is still some issue regarding your endpoint design.
The first intuition that your endpoint give is that product resource could exist in several place.
./orders/{order_id}/products/{prod_id}
./products/{prod_id}
The question you should ask yourself is: Do you really want to refer to product?
Can product be leaving outside of any orders?
Having a resource sitting in 2 different place might not be that great as you are managing 2 different endpoint with similar behavior. Keeping consistency between both endpoint is not that easy.
My 2 cent is to avoid the term product as it can be confused with a single instance of a product. For example if you sell a toothbrush branded AAA, sku 1234 an order is not compose by this product but by one off the item that you have in stock. The item is "instance" of the toothbrush branded AAA, sku 1234.
As I understand your question you are not really referring to a product but more to a stock-item which should be a unique id.
The resource stock-item if you decide to have one should exist prior to the order. I guess the customer is not adding item to your stock and at the same time purchasing this item.
In conclusion I think that you are not creating the stock-item resource at all when creating orders but just making a reference to it.