Sounds like a cool project. I made a really simple app with the movieDB api when I was first learning iOS. I've been meaning to do an app with this API again. Where you can tweet a movie review from the movie app along with the movie poster.
You might be able to get away with just CoreData and a MovieDB client without using PostgreSQL (assuming you're building a native app). But that's just my two cents. I'm still learning!
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