Web App Framework with PostgreSQL + fast + easy

[Ben]

I'm looking for a web application framework with a good interface to
PostgreSQL.

The app I'm developing is relatively simple, but I'm new to coding, so it
needs to be easy.

What I'm making is a wiki-like system that could be thought of as similar
to MediaWiki, but with each word editable separately - ie. edit locks
would be one word at a time.

Features I need:
 * works well with PostgreSQL - fast and powerful with support/awareness
of MVCC
 * easy to use
 * fast

Features I want:
 * flexible options for user accounts, with some reasonable non HTTPS
 security
 * support for internationalisation.

I am a happy Plone user, but I'm concerned it or even Zope on its
own wouldn't be fast enough as they have a whole lot of functionality I
really don't need and aren't built for a RDBMS.

Ben