DataStax Cassandra Developer Certification Certification Questions and Answer (Dumps and Practice Questions)

Question : Vnodes helps Cassandra in which of the following way

A. Tokens are automatically calculated and assigned to each node
B. Rebalancing a cluster is automatically accomplished when adding or removing nodes.
C. Rebuilding a dead node is faster because it involves every other node in the cluster.
D. The proportion of vnodes assigned to each machine in a cluster can be assigned, so smaller and larger computers can be used
in building a cluster


1. A,B,C
2. B,C,D
3. A,B,D
4. A,C,D
5. A,B,C,D

Correct Answer : Get Lastest Questions and Answer :
Explanation: Virtual nodes, known as Vnodes, distribute data across nodes at a finer granularity than can be
easily achieved if calculated tokens are used. Vnodes simplify many tasks in Cassandra:

Tokens are automatically calculated and assigned to each node.
Rebalancing a cluster is automatically accomplished when adding or removing nodes. When a node joins the cluster, it assumes
responsibility for an even portion of data from the other nodes in the cluster. If a node fails, the load is spread evenly
across other nodes in the cluster.
Rebuilding a dead node is faster because it involves every other node in the cluster.
The proportion of vnodes assigned to each machine in a cluster can be assigned, so smaller and larger computers can be used in
building a cluster.





Question : If not using virtual nodes (vnodes), you must calculate tokens for your cluster.

1. True
2. False

Correct Answer : Get Lastest Questions and Answer :
Explanation: : If not using virtual nodes (vnodes), you must calculate tokens for your cluster.




Question : Which all is correct, with regards to Gossip protocol?

A. Gossip is a peer-to-peer communication protocol in which nodes periodically exchange state information about themselves and
about other nodes they know about.
B. The gossip process runs every second and exchanges state messages with up to three other nodes in the cluster.
C. A gossip message has a version associated with it, so that during a gossip exchange, older information is overwritten with
the most current state for a particular node.
D. Every node in the Cluster should work as a seed node


1. A,B,C
2. B,C,D
3. A,C,D
4. A,B,D

Correct Answer : Get Lastest Questions and Answer :
Explanation: : Gossip is a peer-to-peer communication protocol in which nodes periodically exchange state
information about themselves and about other nodes they know about. The gossip process runs every second and exchanges state
messages with up to three other nodes in the cluster. The nodes exchange information about themselves and about the other
nodes that they have gossiped about, so all nodes quickly learn about all other nodes in the cluster. A gossip message has a
version associated with it, so that during a gossip exchange, older information is overwritten with the most current state for
a particular node.

To prevent problems in gossip communications, use the same list of seed nodes for all nodes in a cluster. This is most
critical the first time a node starts up. By default, a node remembers other nodes it has gossiped with between subsequent
restarts. The seed node designation has no purpose other than bootstrapping the gossip process for new nodes joining the
cluster. Seed nodes are not a single point of failure, nor do they have any other special purpose in cluster operations beyond
the bootstrapping of nodes.

Related Questions

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Question : Which of the following is correct for collections in Cassandra table ?

1. Use collections when you want to denormalize a small amount of data.

2. Use collections when you want to store a small amount of data.

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4. 1 and 2

5. 1,2 and 3



Question : Which of the following statement true, with regards to Cassandra Index?


1. An index provides a means to access data in Cassandra using attributes other than the partition key.

2. You can index collection columns

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4. 1 and 2

5. 1 and 3



Question : The more unique values that exist in a particular column, the more overhead you will have, on average, to query
and maintain the index.

1. True
2. False


Question : In which of the following scenario indexes should be avoided?

A. On high-cardinality columns
B. In tables that use a counter column
C. On a frequently updated or deleted column.
D. To look for a row in a large partition unless narrowly queried


1. A,B,C
2. B,C,D
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4. A,C,D
5. A,B,C,D


Question : You have a Books database with following columns

BOOK_TITEL
BOOK_AUTHOR
BOOK_PRIMARY_KEYWORD

Assume, each book is written by individual author and one author has written only one book. Its possible that primary keyword
can be shared among various books. There are almost 10M books in this table. Which of the following is correct with regards to
index?

1. You can create index on both BOOK_AUTHOR and BOOK_PRIMARY_KEYWORD

2. You can create index on BOOK_AUTHOR and avoid on BOOK_PRIMARY_KEYWORD

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4. On millions record table, we should not have index any columns.



Question : You must always create index to frequently updated or deleted column

1. True
2. False