I'm not looking for SSO. Did I use IAM wrongly? I'm talking about tiny apps that do require a protected back-end access, generally for somewhat bootstrapped CSO

I'm not looking for SSO. Did I use IAM wrongly? I'm talking about tiny apps that do require a protected back-end access, generally for somewhat bootstrapped CSOs. Not looking for anything fancy, but rather quick and dirty. For example, updating a SQLite db via gSheets API. PHP as that's default for shared hosting.