[Django]-Django cluster deployment

This sounds like a good setup, although its hard to know exactly what your setup looks like. In terms of memory etc. and what traffic you expect to handle.

You might want to consider using Django’s multidb support and have a read only postgres instance (use DB routing to direct reads to the read only for certain apps). This can offer up some quite nice speed improvements – and at the moment you could have a potential bottleneck at the single postgres instance depending how heavy your database work is.

As @ashwoods suggested, it might be working looking into gunicorn and nginx. I guess at the moment you use Apache only to run mod_wsgi? And lighttpd for the static files? With nginx, you can use it with a number of wsgi servers and its great for static files too.

The setup looks pretty good to me. I would consider using gunicorn/uwsgi + nginx. I would also benchmark using pbbouncer, although pgpool2 offers more out of the box.