Amazon SimpleDB or Amazon RDS? I'm at a deciding point in my project of whether to implement the database using SimpleDB or Amazon RDS. The database needs to be accessed through an iPhone app and as well through a website. Here are some factors I've been considering in the decision:


Amazon has an iOS SDK (Beta) for iPhone that can be used with their SimpleDB --
Getting Started with the AWS SDK for iOS(Beta)
Cost. SimpleDB is practically free while running a small RDS instance is $80/month or around $240/ year. If the price wasn't such a difference I would just choose the RDS and be done with it.
If SimpleDB is all that I require for my app then I am fine using that, but I do not know enough about databases yet (I just began my Database I course today) to decide if it has the functionality I need.


The other thing is that I've already built the website using PHP/MySQL and I really like how easy it is to use this combination so having to re-build it using SimpleDB is kind of annoying.

I think that I should probably just pay the cost for a year's worth of an RDS instance and just be done with it, but I just wanted to see what other people have to say about this.
Well it's really a matter of you deciding on the architecture you want to go with.

SimpleDB is a non-relational "no-sql" data storage system built around the ideas of collections of items accessible via key/value pairing.

Where as RDS is really just a custom version of MySQL which a fully relational SQL database.

both systems will work for tracking profiles but the implementation patterns are very different. Neither is right or wrong, so it's your call on what you want to do.