Hub4TechTop Cassandra Interview Question and Answer

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

Question: 1 Explain what is 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.

Question: 2 List the benefits of using 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

Question: 3Explain what is composite type in Cassandra?

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.

Question: 4 How does Cassandra write?

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.

Question: 5 How Cassandra stores data?

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.

Question: 6Define the management tools in Cassandra.

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

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

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.

Question: 8Define memtable.

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