This presentation covers some aspects of our architecture, highlighting differences between MongoDB and Cassandra. It goes in depth to explain why Cassandra is a better choice for a general purpose Application Platform as well as a Media Buying Analytics tool.
This video goes over common design patterns people might be familiar with coming from a background with MongoDB and highlight how Cassandra would be used as a better alternative. It also discusses cqlengine which is nearing feature completeness as the Cassandra object mapper for Python.
Video producer: http://www.datastax.com/