Question-1: Is this interview Question helps, in preparing the Cassandra administrator or developer certification?

Answer: Certainly, that would help, these interview questions are not only for preparing for a particular interview but also helpful in various situations like

• If you are giving an interview for Cassandra database developer or administration position.
• If you are planning to give Cassandra certification either administration or developer. Preparing the Cassandra certification go through the Question and Answers provided by com. If you want to clear your exam in first attempt.
• If you want to regularly learn or update your skills for Cassandra database then keep reading this Question and Answers on regular basis.

Question-2: What does it mean that Cassandra database is an active anywhere database?

Answer: Cassandra database is deployed in cluster, which usually has more than one node. And this can span across data centers (may be physically separated datacenters) as AWS availability zones. And user can query any node in the cluster which should return the data. Whether it holds or not. If node does not hold the data, it would find it from other nodes.

Question-3: What is the ring?

Answer: In the Cassandra world ring is same as cluster. Collection of nodes grouped together. It is called ring because it works on the concept of the tokens, which decides on which node data should go. Tokens are generally evenly distributed across all the nodes.

Question-4: How Cassandra make sure that the data written on the node cannot be lost and remain durable?

Answer: Cassandra always write data in two places, when first write request is received.

1. Memtable (that is in memory): Stored in the same structure as in SSTable.
2. Commit Log (sequentially data would be persisted on hard disk).

Once it is written on both the places then only Cassandra return successful write acknowledgement to the client.  

Question-5: What protocol is used by Cassandra nodes to share the information with each other?

Answer: Gossip protocol. Using this protocol Cassandra nodes share the information with each other. And learnt about each node in the cluster.