We have uploaded 100k products using our API and have not encountered any SQL timeouts in the backend.
SQL timeouts could be attributed to your SQL configuration, location of your SQL server or your systems configuration.
Also if you encounter anymore issues, can you open a support ticket so we can better identify the problem you are encountering? Please let us know how many products, number of customers, number of orders and images per product you are trying to upload.
the Telerik team
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