[tracker1]

I think that even in a NoSQL driven domain, that a classic SQL based RDBMS has a place. It's that certain types of load have acceptable levels of relaxed constraints.. that can increase when your data is searched/read over 1000 times for every write. That joins are expensive and even mirroring data to a nosql store has benefits over purely rdbms.

I like document stores like MongoDB and RethinkDB and feel they are a great fit for most scenarios. I also feel that caching layers with Redis or Memcached can help...

Cassandra is interesting in the primary storage space as well, and imho has resolved a lot of issues, while others remain. I'm interested to see if this database can get there faster than Cassandra/CQL can get to more parity with traditional SQL systems.

While I appreciate the options, there is no one solution for everything... If you never break 100 simultaneous users, memory-mapped flat files and map/reduce could be sufficient.