We've put Nginx in front of GAE and it works without any issue. I haven't tried any other methods such as Varnish though. We aren't really throwing too much traffic at the GAE app which is "behind" Nginx, but we fully expect it to handle a reasonable amount of traffic.
I'm sure there are many people who have done this. I'd be interested in hearing how other people have solved the lack of SSL...
I'm sure there are many people who have done this. I'd be interested in hearing how other people have solved the lack of SSL...