Well, Redis data structures like lists, sets, hashes and sorted sets are great! You don't have to switch context and think in terms of SQL while programming.
But someone may initially think that Redis can find all items that have 'cactus' in the text, which is not true.
One could say Redis is 'almost' a DB (as per the common conception of a db like MySQL, etc) and more like a 'build your own db' kit.