It's easier to go from something more highly structured to something looser. Start with a relational db and let it grow then pay attention to what data gives yo

It's easier to go from something more highly structured to something looser. Start with a relational db and let it grow then pay attention to what data gives you the most scale pain and try to move that out to Riak / Cassandra / etc... Don't prematurely scale, just pay attention to your metrics, scale vertically first, then tackle the very specific pain points.