Deactivate postgres user account
You might also consider ALTER USER someone WITH NOLOGIN; which is probably the right solution if you have multiple databases in the same back-end and want to block the user entirely.
To lock an account:
# Lock an accountALTER USER someone WITH NOLOGIN;To unlock an account:
# Un-lock an accountALTER USER someone WITH LOGIN;Check account is locked or not:
select rolcanlogin from pg_roles where rolname='database_user';OUTPUT:rolcanlogin------------- f(1 row)f = false # Can not logint = true # Can login
Take a look at the REVOKE command.
In order for a user to connect to a database he has been granted the CONNECT privilege.Just REVOKE this privilege and he won't be able to use this database.