What’s the catch with this thing?

The security model is challenging, as it relies on Postgres users for iam. Your users essentially log directly into your db

You can see what this means specifically from the docs: https://electric-sql.com/docs/guides/auth

Isn’t Postgres a fairly capable IAM provider, all things considered? I’d their access control mechanisms at least as much as a run of the mill external backend’s.

For basic auth it works well, but the challenge comes when you need to integrate with oidc, need to enforce mfa, enable sso etc. session invalidation is also quite complicated.

You need an identity middle man in front of the Postgres identity to tackle these and validate that the session is still active. Last time I looked at electric it was a big challenge to integrate such a service. This might have improved since then however