There are huge overlap between Mongo and Firestore. Mongo gives you the ability to finely control many aspects of the DB (sharing, replication, etc...) where as

There are huge overlap between Mongo and Firestore. Mongo gives you the ability to finely control many aspects of the DB (sharing, replication, etc...) where as Firestore manages it for you. Firestore and DynamoDB are also closed source and you can only run them on their respective cloud providers. I don't have enough direct experience with DynamoDB to give you an accurate comparison.