I have figured out what you say redis, but has changed a lot since 2009. Basically I'm a rails developer so my I usually prefer ActiveRecord.. Mysql or Postgre

I have figured out what you say redis, but has changed a lot since 2009. Basically I'm a rails developer so my I usually prefer ActiveRecord.. Mysql or Postgres. However I have noticed that redis is becoming a very good alternative to the persistent storage in term of hot cache(like twitter) when you have heavy writes not only for cache the data after the first read(like rails in memcache). Another interesting feature, in the next release, is the support for geospatial