AWS Shiny keyring - no way?

...So I have Shiny application with Postgres backend located on AWS. I need my application to store database credentials somewhere(?) and these credentials should be retrieved by app code when user clicks 'login' button.
I read that when R is running on Linux server, backend_secret_service API is not available, so the only option is backend file;
But I also found that file-based keyring needs to be unlocked interactively every time the new R session starts. Even if I create a keyring with empty password, regardles of being system or custom keyring, when I re-start R session and try to call get_key, it asks for password.
So that means the stored key CANNOT be retrieved by Shiny application from AWS file keyring programmatically, without entering password manually.
So much about storing credentials from R on AWS?