I have a computer science degree from Harvard, and have been a software developer for over a dozen years. I have become an adept web developer in the past 4 years, having designed & built 5 platforms from scratch in that time.
I've designed & built the databases for all those platforms, and all of them used MongoDB as the primary database (with some of them using Redis as a secondary system). I DO NOT have any experience with Cassandra, though I have tons of experience with Mongo.
If you think this might be at all useful to you, please don't hesitate to reach out. I would, of course, need to know exactly what it is that you need to analyze before accepting this project, and would love to have a conversation with you to figure this out.