Truth about joins: Google app engine datastoreâ€™s limitation of not allowing joins might soon be a thing of the past. Simple joins may now be possible on GAE if you are using Java. Its still beta, but the fact that this is being tested is very encouraging.
Redis real-life examples [More here] : Iâ€™ve been seeing a lot of discussions around Redis lately. Here are some use cases Iâ€™ve gathered from a couple of posts. Havenâ€™t yet seen it being used by a large organization.
Using Varnish to assist with AB testing â€“ Testing new uncooked features by external customers get more difficult as products become more mature and stable. Tools like â€œvarnishâ€ could be used to test different pages/features.