DynamoDB vs MongoDB NoSQL

Question

I'm trying to figure out what can I use for a future project, we plan to store about 500k records per month in the first year and maybe more for the next years this is a vertical application so there's no need to use a database for this, that's the reason why I decided to choose a NoSQL data storage.

The first option that came to my mind was mongo DB since is a very mature product with a lot of support from the community but in the other hand we got a brand new product that offers a managed service at top performance, I'll develop this application but there's no maintenance plan so I think that will be a huge advantage since amazon provides an elastic way to scale.

My major concern is about the query structure, I haven't looked at the dynamo DB query capabilities yet but since is a k/v data storage I feel that this could be more limited than mongo DB.

If someone had the experience of moving a project from MongoDB to DynamoDB, any advice will be totally appreciated.