[Ixiaus]

Riak is amazing and actually scales. But I would only use Riak for high-volume data storage (similar to S3).

FoundationDB looks great, I haven't used it yet but they appear to have their heads on right.

PostgreSQL, the newer versions, have indexable BJSON data types so you can get the same exact behavior from Postgres as you do from Mongo but with a true RDBMS along with it, a dependable storage engine, etc...

Postgres is harder to scale horizontally though - if you have really high-volume data writes, you should be using something else for that.

I typically use PostgreSQL for all of my highly "structured" data and Riak for high-volume and "flatter" data (Postgres also often serves as an index into those objects).

[tannerj]

Awesome, Thanks for the reply. My use cause is barely out of the "toy app" range. We only do a handful of events each year and they only draw around 100 attendants. We're talking a very small amount of data. When you do the PostgreSQL and Riak combo is it ever on the same/related dataset. What are you using at the application layer? I'm building this in rails and I feel like it would be better to store the structured fields in MySQL and the variant data in something NoSQL. But I haven't read much into using active record with two different persistence layers. That's interesting about PostgreSQL with indexable BJSON. I've only ever used MySQL, I really need to check out Postgres.

[Ixiaus]

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.