Upsert rows in a Salesforce Marketing Cloud Data Extension using the REST API with batching

In-depth guide

Steps

1. Identify the Data Extension's External Key (visible in Email Studio > Data Extensions > Properties).
2. POST to {rest_instance_url}/hub/v1/dataevents/key:{externalKey}/rowset with a JSON body containing an array of row objects; each row must include all primary key fields.
3. The rowset endpoint performs an upsert: it inserts a row if the primary key is absent and updates if it exists — confirm the DE's primary key fields before upserting.
4. Batch rows in groups of up to 2,500 per request to stay within payload size limits; handle 429 rate-limit responses with a retry strategy.
5. Confirm the response status: 200 with no body indicates success; errors return a JSON body with a message describing the issue.
6. For asynchronous large-batch ingestion, consider the Bulk Import via Automation Studio or the /async/dataevents endpoint instead of synchronous rowset calls.