Cassandra Interview Questions and Answers

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Top Cassandra Interview Question and Answer

• Hub4Tech

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Question 1 Explain what is Cassandra?

• Answer
• Cassandra is an open source data storage system
  developed at Facebook for inbox search and
  designed for storing and managing large amounts
  of data across commodity servers. It can server
  as both
• Real time data store system for online
  applicationsAlso as a read intensive database
  for business intelligence system

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Question 2 List the benefits of using Cassandra.

• Answer
• Unlike traditional or any other database, Apache
  Cassandradelivers near real-time performance
  simplifying the work of Developers,
  Administrators, Data Analysts and Software
  Engineers.
• Instead of master-slave architecture, Cassandra
  is established on peer-to-peer architecture
  ensuring no failure.
• It also assures phenomenal flexibility as it
  allows insertion of multiple nodes to any
  Cassandra cluster in any datacenter. Further, any
  client can forward its request to any server.

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Question 3Explain what is composite type in
Cassandra?

• Answer
• In Cassandra, composite type allows to define key
  or a column name with a concatenation of data of
  different type. You can use two types of
  Composite Type
• Row Key
• Column Name

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Question 4 How does Cassandra write?

• Answer
• Cassandra performs the write function by applying
  two commits-first it writes to a commit log on
  disk and then commits to an in-memory structured
  known as memtable. Once the two commits are
  successful, the write is achieved. Writes are
  written in the table structure as SSTable (sorted
  string table). Cassandra offers speedier write
  performance.

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Question 5 How Cassandra stores data?

• Answer
• All data stored as bytes
• When you specify validator, Cassandra ensures
  those bytes are encoded as per requirement
• Then a comparator orders the column based on the
  ordering specific to the encoding
• While composite are just byte arrays with a
  specific encoding, for each component it stores a
  two byte length followed by the byte encoded
  component followed by a termination bit.

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Question 6Define the management tools in
Cassandra.

• Answer
• DataStaxOpsCenter internet-based management and
  monitoring solution for Cassandra cluster and
  DataStax. It is free to download and includes an
  additional Edition of OpsCenter
• SPM primarily administers Cassandra metrics and
  various OS and JVM metrics. Besides Cassandra,
  SPM also monitors Hadoop, Spark, Solr, Storm,
  zookeeper and other Big Data platforms. The main
  features of SPM include correlation of events and
  metrics, distributed transaction tracing,
  creating real-time graphs with zooming, anomaly
  detection and heartbeat alerting.

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Question 7 Mention what are the main components
of Cassandra Data Model?

• Answer
• The main components of Cassandra Data Model are
• Cluster
• Keyspace
• Column
• Column Family

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Question 8Define memtable.

• Answer
• Similar to table, memtable is in-memory/write-back
  cache space consisting of content in key and
  column format. The data in memtable is sorted by
  key, and each ColumnFamily consist of a distinct
  memtable that retrieves column data via key. It
  stores the writes until it is full, and then
  flushed out.

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