Thanks man :)

> > proxy_buffers 8 2m;
> > proxy_buffer_size 10m;
> > proxy_busy_buffers_size 10m;
>
> Buffers used looks huge, make sure you have enough memory.

Mmmhhh, do you think I should remove these and trust nginx's default values for these buffer?

> > proxy_cache one;
> > proxy_cache_key "$request_uri|$request_body";
>
> Usuing request body as a cache key isn't really a good idea unless
> all request bodies are known to be small.

Ok, I changed that to:
proxy_cache_key "$scheme$host$request_uri";

I also made few additions under location/:

proxy_cache_valid 200 302 304 10m;
proxy_cache_valid 301 1h;
proxy_cache_valid any 1m;

proxy_next_upstream error timeout invalid_header http_500 http_502 http_503 http_504 http_404;

Do you think these are good and justified?

Unfortunately I'm seeing these warnings now:
"an upstream response is buffered to a temporary file"

Any hints why? Help is much appreciated

Cheers
Michael