Numerical Data - High Volume + High Velocity + Fast Retrieval
As storage engine or Handling velocity of data, Cassandra and Hadoop will pass with flying colors.
Now coming into real time part, Cassandra can provide you a near real time solution, where as Hadoop alone is not enough (batch nature, map-reduce jobs). You can try with Hadoop with Storm, that will give you near real time capability, but it will increase the complexity of the solution (using spouts and bolts). Also you can try some rule engine, which will provide you an added advantage towards real time solution.