Mod_redis
github.com
github.com
There also is a nginx module compatible with redis2 protocol : https://github.com/agentzh/redis2-nginx-module
i wonder if you can mix this with an auth module somehow.
it probably needs a way to do logging and/or multiple commands (you could send a PUB message beforehand and log elsewhere)
There'd be no practical way of reproducing someone else's auth key without knowing their username and password, so this setup would be basically secure as long as the application is designed in such a way that either client-side Redis requests are read-only or that it isn't dangerous for any user to have write access to their own data.
you don't really even need an auth key, just a session key?
one other problem is csrf issues.
It looks like Webdis has support for basic access control, but I'm not 100% clear on how well it would work for securely throwing database logic into the client: http://webd.is/#acl
Also, while not related to Redis, this similar project looks pretty sexy: https://github.com/thurloat/httpdb
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Edit:
I haven't tested Webdis, but since HTTPDB has a publicly available version for testing, I decided to play around with it, and here's one way my auth key idea could be made to work pretty simply:
http://httpdbapp.appspot.com/set/address:AUTH/1000%20Wrong%2...
http://httpdbapp.appspot.com/get/address:AUTH
The main danger here is that it doesn't look like there's any sort of protection against malicious users filling the database with junk data to run up your GAE quota, or potentially overwriting non-private values and messing up random parts of the application.
Also, I just noticed that the last commit was two years ago, so I'll look around to see if something similar but more secure is out there.