Sharepoint REST API file upload is atomic ?

Hello
I am using sharepoint rest api to upload files in Sharepoint using this documentation.
Everything works but I want to make sure that I compeletly understand the behavior.

Does the file become immediately available in sharepoint folder once I start the upload or does it wait for the upload to complete before becoming available to be read ?
I want to make sure that other users do not start reading my file while it's still loading or while it's still incomplete.

endpoint used for file upload:

POST https://{site_url}/_api/web/GetFolderByServerRelativeUrl('Folder Name')/Files/add(url='a.txt',overwrite=true)

Thanks in advance.