MongoDB: https://en.wikipedia.org/wiki/MongoDB

Apache Cassandra:https://en.wikipedia.org/wiki/Apache_Cassandra

Cassandra is a scalable key-value store columnar NoSQL database that can be highly available. Cassandra suffers from a lack of performance caused by the requirement to store data on disk. In addition, Apache Cassandra is limited by:

-Not supporting ACID transactions
-Not offering an in-memory computing option
-Lack of SQL support. No SQL operations such as joins, aggregations, groupings or indexes
-No ad hoc query capabilities

However, inserting the GridGain in-memory computing platform between Apache Cassandra and an application provides Cassandra transactions and the following capabilities for the portion of the data stored in GridGain:

-Cassandra transactions across the distributed architecture including ACID transaction support
-A 1,000x query speed improvement from in-memory computing
-Read-through and write-through data from and to Cassandra
-ANSI SQL-99 compliance to run ad hoc and structured queries