As of the latest available information, Apple does not directly provide an endpoint for checking refund history for multiple transactions in a single request via their App Store Server API. The endpoint
https://api.storekit.itunes.apple.com/inApps/v2/refund/lookup/{transactionId}
allows you to check the refund status for a single transaction ID at a time. What if you have 8000 subscribers? Are we going to send 8k requests everyday? What's the solution for this scenario? We don't want to implement the notifications by the way. Any solutions?
As you stated, the recommended way is to implement App Store Server Notifications. Apple does not recommend polling our APIs in any scenario, including checking the refunds status of active subscriptions. The rate limit for the Get Refund History endpoint is 10 requests per second, which equates to 864,000 requests per day.