Apache Cassandra™ 3.x Developer Associate Certification is the ideal foundational certification exam for developers looking to test their Apache Cassandra™ expertise. Focused on fundamental Apache Cassandra™ knowledge, this exam will set you on the pathway to join thousands of engineers already certified on the industry’s most popular, massively scalable NoSQL database.

Learn Cassandra topics, first of all, using dedicated training path on official DataStax academy site

The last step is "Test Your Self" with 90 questions splitted into 3 Practice Tests

Good luck!