From https://blog.pythian.com/cassandra-use-cases/

“The ideal Cassandra application has the following characteristics:

• Writes exceed reads by a large margin.
• Data is rarely updated and when updates are made they are idempotent.
• Read Access is by a known primary key.
• Data can be partitioned via a key that allows the database to be spread evenly across multiple nodes.
• There is no need for joins or aggregates.

Some of my favorite examples of good use cases for Cassandra are:

• Transaction logging: Purchases, test scores, movies watched and movie latest location.
• Storing time series data (as long as you do your own aggregates).
• Tracking pretty much anything including order status, packages etc.
• Storing health tracker data.
• Weather service history.
• Internet of things status and event history.
• Telematics: IOT for cars and trucks.
• Email envelopes—not the contents.”