I've used mongodb for a recent prototype. It was brilliant, I iterated through the data model as I coded. However, I am now very aware that I have an implicit

I've used mongodb for a recent prototype. It was brilliant, I iterated through the data model as I coded. However, I am now very aware that I have an implicit schema in my code that will be harder to understand in 6 months than a database schema. I traded fantastic flexibility in initial development against easily maintained longevity. I suspect I will move to something more relational but have also taken on the need to really understand the trade-offs I'm making. I've started reading Seven Databases in Seven Weeks to fill in some of my gaps.