Engineering Questions with Answers - Multiple Choice Questions
MCQs on Cassandra with Hadoop – 1
1 - Question
A _________ grants initial permissions, and subsequently a user may or may not be given the permission to grant/revoke permissions.
a) keyspace
b) superuser
c) sudouser
d) none of the mentioned
View Answer
Answer: b
Explanation: Object permission management is based on internal authorization.
2 - Question
Point out the correct statement.
a) Cassandra accommodates expensive, consumer SSDs extremely well
b) Cassandra re-writes or re-reads existing data, and never overwrites the rows in place
c) Cassandra uses a storage structure similar to a Log-Structured Merge Tree
d) None of the mentioned
View Answer
Answer: c
Explanation: A log-structured engine that avoids overwrites and uses sequential IO to update data is essential for writing to hard disks (HDD) and solid-state disks (SSD).
3 - Question
__________ is one of many possible IAuthorizer implementations and the one that stores permissions in the system_auth.permissions table to support all authorization-related CQL statements.
a) CassandraAuth
b) CassandraAuthorizer
c) CassAuthorizer
d) All of the mentioned
View Answer
Answer: b
Explanation: Configuration consists mainly of changing the authorizer option in the cassandra.yaml to use the CassandraAuthorizer.
4 - Question
Cassandra creates a ___________ for each table, which allows you to symlink a table to a chosen physical drive or data volume.
a) directory
b) subdirectory
c) domain
d) path
View Answer
Answer: b
Explanation: The new file name format includes the keyspace name to distinguish which keyspace and table the file contains when streaming or bulk loading data.
5 - Question
Point out the wrong statement.
a) Cassandra provides fine-grained control of table storage on disk, writing tables to disk using separate table directories within each keyspace directory
b) The hinted handoff feature and Cassandra conformance and conformance to the ACID
c) Client utilities and application programming interfaces (APIs) for developing applications for data storage and retrieval are available
d) None of the mentioned
View Answer
Answer: b
Explanation: The hinted handoff feature and Cassandra conformance and non-conformance to the ACID.
6 - Question
When ___________ contents exceed a configurable threshold, the memtable data, which includes indexes, is put in a queue to be flushed to disk.
a) subtable
b) memtable
c) intable
d) memorytable
View Answer
Answer: b
Explanation: You can configure the length of the queue by changing memtable_flush_queue_size in the cassandra.yaml.
Explanation: You can configure the length of the queue by changing memtable_flush_queue_size in the cassandra.yaml.
7 - Question
Data in the commit log is purged after its corresponding data in the memtable is flushed to an _________
a) SSHables
b) SSTable
c) Memtables
d) None of the mentioned
View Answer
Answer: b
Explanation: SSTables are immutable, not written to again after the memtable is flushed.
8 - Question
For each SSTable, Cassandra creates _________ index.
a) memory
b) partition
c) in memory
d) all of the mentioned
View Answer
Answer: b
Explanation: Partition index is list of partition keys and the start position of rows in the data file (on disk).
9 - Question
Cassandra marks data to be deleted using _________
a) tombstone
b) combstone
c) tenstone
d) none of the mentioned
View Answer
Answer: a
Explanation: Cassandra also does not delete in place because the SSTable is immutable.
10 - Question
Tombstones exist for a configured time period defined by the _______ value set on the table.
a) gc_grace_minutes
b) gc_grace_time
c) gc_grace_seconds
d) gc_grace_hours
View Answer
Answer: c
Explanation: During compaction, there is a temporary spike in disk space usage and disk I/O because the old and new SSTables co-exist.