Just curious, what would be the major drawbacks of not using relational here? My understanding is that AWS is pushing Dynamo quite a bit and it seems cheaper, so if they're only needing to query off of session id and maybe user id, shouldn't that be sufficient?
Relational is super handy. Very easy to report on and do various things down the road.
If all he needed was session id, sure, NoSQL is more or less the same. But what about when he adds other fields that are related? Say customer address or reports or .... His life may very well be easier with relational.
You should generally start relational. Then branch out if you are hitting the brick walls of relational. People using NoSQL for a 100MB database are making their life SERIOUSLY more difficult than it needs to be. (I have done it before, not fun).
1) A NoSQL DB for the main data providing replication and scalability(e.g. Cassandra or DynamoDB).
2) Another DB for quick access and transient Data where replication is not so important, e.g. storing the session cookie. Relational vs Non-relational would not be an issue since I'm only storing very little data here and want fast access and minimize costs(in DynamoDB you still have to pay per operation). Therefore I'm looking for some simple solution like ElastiCache.
I'm doing a social networking site, so I don't know how much data I will end up with. My reasoning was as follows:
1) The data model is rather simple, basically one table with the user data(name, location, age, etc...) and some images. So it shouldn't be too difficult to do this with NoSql as opposed to SQL. Yes, simpler with SQL but not significantly so.
2) If I ever need to scale, I'd rather make the right choice from the beginning(NoSQL) so as not to need a migration later.
3) In any case NoSQL would be a learning experience for me, so another plus.
If there is a mistake in my reasoning I would be grateful for any one pointing it out.