Hey there! We've found the following might help you get unblocked faster:

• 🧵 Authentication is suddenly failing for Postgres user

• 🧵 Locked Out of Postgres After Password Change – Need Urgent Access to Data

• 🧵 password authentication failed for user "postgres"

If you find the answer from one of these, please let us know by solving the thread!

Is this a new user in n8n or a new user within the postgres instance?

its a new user in postgres instance, and the postgrest instance setting -> database -> credentials : there is only postgres user name and password

these threads doesn't solve

If you wish to change the username/password or create a new pg user, you must do so via SQL queries within the database. The user/pass env vars are only used to create the user when the database is first created.

and after i create "new_user" from remote_cli from postgres railway instance, i can't see the new_user appearing at railway's postgres instance in dashboard, or railway its only strick to "postgres" user , its not allow for other user ?

example, i create "new_user" and database "bookdb" for "new_user", but i can't login as this user via DATABASE_PUBLIC_URL (postgresql://new_user:new_user_pw@switchback.proxy.rlwy.net:22384/bookdb), n8n's postgres node ( i only can login with this "new_user" via remote cli from postgres railway instance, and in n8n can only use "postgres" crendentials)

could you confirm the new_user was created using the encryption method SCRAM-SHA-256

Per above suggestion, try checking the deploy logs for your Postgres instance and see if there are messages that say User "new_user" does not have a valid SCRAM secret.

If that's the case, you can resolve by signing in as postgres user and:
ALTER SYSTEM SET password_encryption = 'scram-sha-256'; -- this changes encryption to SCRAM-SHA-256

SELECT pg_reload_conf(); -- this reloads pg with new config

alter role new_user with password '123456'; -- this sets password for user with SCRAM-SHA-256

appreciate for you've provide extra details bro.