Where are uploaded files stored before importing assets?

Summary:

Hi,

I can import assets using the APIs below. Before importing, I upload the assets CSV file using:
https://___.bigmachines.com/rest/v17/files

From the response, I take the file name and pass it to the import API:
https://___.bigmachines.com/rest/v17/assets/actions/import

Everything works fine, but I need to know where the uploaded files are stored before they are imported. Are they stored on the server or elsewhere?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):