I am stuck in deciding how to implement the below scenario in my application (Spring boot + angular).

1. User will upload a file with email ids (max records estimated is 10k) could be multiple times a month. Each file is a complete data set so we can delete the older records and insert the latest file as the fresh data set.
2. For each email id we have to find the country of the user from a rest api.

I thought the below logic:

1. Each time a user uploads this file store it in cloud storage.
2. Run a batch to delete all existing records from table, read the file and insert all records.

In this scenario i will have to loop in and hit the service for all 10k records to get the user country which i think is not ideal.
Can someone please let me know how can i handle this use case. Can i just find the difference in data and use that? Or any other way you see this can implemented?