Shopify provides a limit for the stores to add products via API (apps) once 50,000 variants are added. After this threshold is reached, no more than 1,000 new variants can be created per day. In certain cases, Shopify needs to enforce rate limiting in order to prevent abuse of the platform.
More information here - https://help.shopify.com/en/api/reference/rest-admin-api-rate-limits#resource-based-rate-limits
Note - These limits don't apply to stores on the Shopify Plus plan.
