Modern PaaS is tough because there's a general expectation that users (and agents) are able to see and read back environment variables in their management UI or CLI - which means that you can't segregate credential values from the public web environment. See e.g. the visibility icons on https://northflank.com/docs/v1/application/secure/inject-sec...

And sure, you can encrypt at rest, and perhaps even enforce that only re-encrypted versions are ever seen by the management/API web server. But fundamentally this display requirement means that if your management/API web server is compromised, users' secrets can be obtained by a process of impersonation.