Rest API to create Sales Order for more than 2k lines is always failing

we have a requirement to process orders containing a large number of line items, with an average volume of up to 3,000 lines per order.
While testing the creation of such orders via the REST API using Postman—with a payload of approximately 2,000 lines (~4MB)—we consistently encountered errors.

[CDATA[CASDK-0041: An error occurred while invoking the REST endpoint.[[java.util.concurrent.TimeoutException: Stream closed: read timeout]].The 500 Internal Server Error is a very general HTTP status code that means something has gone wrong on the server side, but the target service could not be more specific on what the exact problem is. Try invoking the target service using cURL. If the problem persists, contact the target service admin.]