Overall, the product is a little hard to deal with when it comes to upgrading as there are always new versions released every quarter. Also, it’s backup and restore processes are still in their baby steps.
Cassandra has already been integrated into our environment. It has performed well and lived up to the requirements of the highly scalable application which the designers strived to achieve. It has performed admirably as a data store and a huge volume of transaction data is written to Cassandra per second. So it is quite natural to be renewed given its impact.
In our POC Cassandra satisfies all our needs and expectations. We would like to do an additional POC to test its cross-continent cluster level replication features, measuring the performance and data consistency level to help us finally decide how to move to production.
I would give Cassandra a higher rating only if managing a cluster becomes easier. Currently we need a team of at least 2-3 people to manage a 10+ node cluster. The cluster needs a lot of maintenance, cleaning up, monitoring and basically demands much attention. We would basically need a dedicated resource just for managing a Cassandra cluster. If more of these simple tasks get automated we can slim down a team to manage a cluster.
I've used Cassandra for 4 years now, on 3 major projects (one of them truly web-scale), and I'm deeply satisfied. These days, it's my go-to database. That said, technology moves quickly, and it's good to keep abreast of new developments...
I would recommend Cassandra DB to those who know their use case very well, as well as know how they are going to store and retrieve data. If you need a guarantee in data storage and retrieval, and a DB that can be linearly grown by adding nodes across availability zones and regions, then this is the database you should choose.
This rating is solely based on personal experience. Especially since a lot of companies are moving towards noSQL solution, it is worth it to give Cassandra a shot. A lot of open source developers are working hard to make it more efficient.
I think this question is only relevant to user using the enterprise version. We are using the open-source (community) version, so renewal is not really an issue. We are happy with Cassandra and it serves its original purpose.