Realtime Apache Cassandra Multiple choice Questions and Answers pdf

11: Talk about the concept of tunable consistency in Cassandra.
Tunable Consistency is a characteristic that makes Cassandra a favored database choice of Developers, Analysts and Big data Architects. Consistency refers to the up-to-date and synchronized data rows on all their replicas. Cassandra’s Tunable Consistency allows users to select the consistency level best suited for their use cases. It supports two consistencies – Eventual Consistency and Strong Consistency.

12: What are the three components of Cassandra write?
The three components are:
Commitlog write
Memtable write
SStable write
Cassandra first writes data to a commit log and then to an in-memory table structure memtable and at last in SStable.

13: Explain zero consistency.
 In zero consistency the write operations will be handled in the background, asynchronously. It is the fastest way to write data.

14: Mention what are the values stored in the Cassandra Column?
There are three values in Cassandra Column. They are:
Column Name
Value
Time Stamp

15: What do you understand by Kundera?
Kundera is an object-relational mapping (ORM) implementation for Cassandra which is written using Java annotations.

16: What is the concept of SuperColumn in Cassandra?
Cassandra SuperColumn is a unique element consisting of similar collections of data. They are actually key-value pairs with values as columns. It is a sorted array of columns, and they follow a hierarchy when in action.

17: When do you have to avoid secondary indexes?
Try not using secondary indexes on columns containing a high count of unique values as that will produce few results.

18: List the steps in which Cassandra writes changed data into commitlog?
Cassandra concatenates changed data to commitlog. Then Commitlog acts as a crash recovery log for data. Until the changed data is concatenated to commitlog, write operation will never be considered successful.

19: What is the use of “ResultSet execute(Statement statement)” method?
This method is used to execute a query. It requires a statement object.

20: What is Thrift?
Thrift is the name of the Remote Procedure Call (RPC) client used to communicate with the Cassandra server.

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