@jr0cket thanks a lot for your answers 
Today I found Malcolm’s newest screencast about juxt/site while trying to find out if juxt/yada is still “alive”.
I guess I would need to invest several days to wrap my head around juxt/site. Therefore I’m trying to find an off-the-shelf API generation tool. Hasura looks promising, but it may be too sophisticated for my use case. The planned API would allow third parties to schedule social media posts. But I’m not planning to expose a lot of our database via the API.
In Malcolm’s screencast, I find this slide pretty interesting:
(Building Site: Episode 40 - YouTube)
It’s about that juxt/site can just be used as the “auth server” which handles all the complicated OpenID and OAuth2 things. While the API of your app would just receive a JWT. Buying an “auth server as a service” would greatly reduce the cost of my project. Currently, I’m looking into the following:
(Machine to Machine (M2M) Communication - Auth0)
Sounds like an “auth server as a service”. But the documentation after the sign-up is not super helpful. I’m currently watching a few tutorial videos on Youtube about this feature of auth0.com