This is a great example of not understanding the scaling problem of IoT. Not only is the above (quasi-)transaction rate modest by IoT system standards today, but Cassandra is not doing real-time analysis or ad hoc querying of complex relationships across those transactions at the same time, which is usually a requirement.
I know of a production IoT system in the private sector that does 1.5 trillion (quasi-)transactions every 10 minutes, so almost three orders of magnitude higher throughput. Cassandra is an okay choice for storing IoT data but it isn't real-time in the sense that you can do immediate, fast queries about the relationships across those records as they are hitting the system.
"Cassandra [...] isn't real-time in the sense that you can do immediate, fast queries about the relationships across those records as they are hitting the system."
That depends on how you are using Cassandra. Typically, you are expected to know your query patterns up front, and so you will lay your data out accordingly when ingesting. When done properly, this allows for ~1ms queries that return completely up-to-date results.
I know of a production IoT system in the private sector that does 1.5 trillion (quasi-)transactions every 10 minutes, so almost three orders of magnitude higher throughput. Cassandra is an okay choice for storing IoT data but it isn't real-time in the sense that you can do immediate, fast queries about the relationships across those records as they are hitting the system.