Our recommendation is to use the product catalog upload rather than APIs. A couple of additional things to consider: The product catalog is the more performant option. Especially when uploading a large set of products or when the catalog is uploaded frequently, daily as an example with 40K+ products.  If the s3 bucket is has a qualified URL and public access, then I believe it should work. Additionally, we have customers who are sending us data in an alternative format that our services team transcribes into the format the product import can consume. This could be another option. I hope that helps.    ... View more