[abolibibelot]

I'm not sure switching to a document model with multiple indexes (MongoDB) to a key/value store (Redis) is something that can be done easily "later on".

[pothibo]

Well structure evolves over time. Probably the structure would move and you would use redis as a memcache layer (to update counts, notifications, etc). What I'm saying is that databases needs evolves over time.

Comparing in-memory storage with SQL and NoSQL isn't a useful and misses the point.

[ihsw]

Redis is far more than a simple KV store.