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This article was published as a part of the Data Science Blogathon.


HBase is a column-oriented non-relational database management system that operates on Hadoop Distributed File System (HDFS). HBase provides a fault-tolerant manner of storing sparse data sets, which are prevalent in several big data use cases. It is ideal for real-time data processing or random read/write access to large data volumes. In contrast to relational databases like SQL, HBase doesn’t provide a structured query language like those provided by that database.


HBase is a data model that works like Google’s “big table” to make it easy to get to a lot of structured data quickly. It comprises a set of tables that store data in a key-value format. Programmers can use Hbase’s APIs in whatever programming language they want. Data in the Hadoop File System may be read and written in real time using this element of the Hadoop ecosystem.

Either directly or via HBase, data may be stored in HDFS. The data consumer uses HBase to read/access HDFS data at random. Read and write access to the Hadoop File System is provided by HBase.


Any number of columns can be added to the horizontal scalability at any moment.

A multidimensional sorted map is indexed by row key, column key, and timestamp in a distributed manner.

In the case of a system breach, an administrator can use automatic failover to automatically transition data handling to a standby system.

Built on top of the Hadoop Distributed File System, each command and Java code implements Map/Reduce internally to complete the operation.

Frequently referred to as a key-value store, column family-oriented database, or for storing versioned maps of maps.

It is basically a system for storing and retrieving data with random access.

It does not impose relationships between data elements.

It is intended to run on a cluster of commodity hardware-based computers.

Interview Questions

1. What is Apache HBase’s purpose?

Apache HBase is used when random, real-time read/write access to Big Data is required. The objective of this project is to host tables with billions of rows and millions of columns on clusters of commodity hardware. Apache HBase is a distributed, versioned, non-relational, open-source database inspired by Google’s Bigtable: A Distributed Storage System for Structured Data by Chang et al. Apache HBase delivers Bigtable-like functionality on top of Hadoop and HDFS, much as Bigtable utilizes the distributed data storage provided by the Google File System.

2. What are the major elements of HBase?

Major elements of HBase are:

Zookeeper: It performs coordination work between the client and HBase Master.

HBase Master: HBase Master keeps an eye on the Region Server.

RegionServer: RegionServer is responsible for monitoring the Region.

Region: It contains both the in-memory data store (MemStore) and the Hfile.

Catalog Tables: Tables in catalogs consist of ROOT and META.

3. Examine the purpose of filters in HBase.

Filters were added to Apache HBase 0.92 to make it easier for users to access HBase through Shell or Thrift. As a result, they handle your server-side filtering requirements. There are also beautifying filters, which allow you to get more control over the data produced by filters. Here are some HBase filter examples:

Bloom Filter: A space-efficient means of determining if an HFile contains a given row or cell, it is typically used for real-time queries.

Page Filter: The Page Filter can optimize the scan of particular HRegions by accepting the page size as a parameter.

4. How does HBase handle a failed write?

In big distributed systems, failures are common, and HBase is no exception.

If the server hosting a MemStore that has not yet been drained crashes. The data in memory, but not yet persisted, are gone. HBase prevents this by writing to the WAL before the write operation is finished. Every server included in the.

5. Describe deletion in HBase. What are the three types of tombstone markers supported by HBase?

When a cell is deleted in HBase, the data is not truly removed; instead, a tombstone marker is placed, rendering the deleted cell inaccessible. HBase that has been deleted is removed during compactions.

There are three types of tombstone markers:

Version delete marker: It identifies a single version of a column for deletion.

Column delete marker: It flags for deletion of every version of a column.

Family delete marker: It flags every column in a column family for deletion.

6. How does HBase compare to Cassandra?

Cassandra and HBase are both NoSQL databases, a word that has several definitions. Typically, it indicates that SQL cannot be used to manipulate the database. Nonetheless, Cassandra has implemented CQL (Cassandra Query Language), whose syntax is evidently based on SQL.

Both are intended to manage enormous data collections. According to the HBase documentation, an HBase database should include hundreds of millions or, preferably, billions of records. If not, you should continue with a relational database management system.

Not just in terms of how data is kept but also in terms of how the data may be accessed; both are distributed databases. Clients can connect to any cluster node and have access to any data.

HBase lacks native support for secondary indexes but provides a range of methodologies that enable secondary index functionality. These are outlined in the online reference guide for HBase and the HBase community.

7. What happens when the block size of a column family in a previously populated database is altered?

When you modify the block size of a column family, the new data will occupy the new block size, but the old data will stay in the old block size. In the course of data compression, old data will adopt the new block size. As new files are flushed, their block size will change, although current data will remain accurately read. After the next major data compression, all data must be converted to the new block size.

8. Why would you use HBase?

High storage capacity system

Distributed layout to accommodate big tables

Column-Oriented Stores

Horizontally Scalable

Superior functionality & Availability

HBase aims for at least millions of columns, thousands of versions, and billions of rows.

Unlike HDFS (Hadoop Distributed File System), it provides CRUD operations in random real-time.

9. What is the Hbase standalone mode?

This option can be enabled when users do not require Hbase to access the HDFS. It is basically a default mode in Hbase, and users are typically allowed to use it whenever they choose. When the user selects this option, the Hbase uses a file system rather than HDFS.

It is possible to save a significant amount of time by using this mode when doing some key activities. During this mode, you may also impose or remove various time constraints on the data.

10. Contrast HBase and Hive?

Hive can enable SQL-savvy users to perform MapReduce jobs. Since it is JDBC-compliant, it is also compatible with current SQL-based applications. Since Hive queries traverse all of the table’s contents by default, their execution may be time-consuming. Nonetheless, Hive’s partitioning function can restrict the volume of data. Partitioning enables the execution of a filter query across data stored in distinct folders and the reading of just the data that matches the query. It might be used, for instance, to only process files generated between specific dates if the file names contain the date format.

HBase operates by storing data as key/value. It provides four core operations: put for adding or updating rows, scan for retrieving a range of cells, get for returning cells for a particular row, and delete for removing rows, columns, or column variants. Versioning is provided to retrieve past data values (the history can be deleted now and then to clear space via HBase compactions). Although HBase contains tables, a schema is necessary only for tables and column families but not for individual columns, and increment/counter functionality is supported.

MapReduce tasks operate on Hive, a SQL-like engine; HBase, a NoSQL key/value database, runs on Hadoop.


This article provides information about HBase, a column-oriented non-relational database management system, and covers a variety of topics, I hope that this information was useful and that you are now more prepared for the next interviews. Here are some of the article’s most salient points:

What is HBase, and what are its features?

HBase filters and modes are available.

HBase comparisons with Hive and Cassandra, as well as many other topics at the basic, intermediate, and tough levels.

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Microsoft’s Power Bi Interview Questions

This article was published as a part of the Data Science Blogathon.


Microsoft’s Power BI is one of its rapidly growing corporate analytics services. This self-service business intelligence tool is the latest and greatest in the data-driven industry. It eased the workaround for attaining data from several sources and consolidating it into one management tool.

Many of the world’s leading companies use Microsoft Power BI to gain superior business insights. In addition, Microsoft Power BI has been positioned in Gartner’s Magic Quadrant for the fifteenth year as premier analytics and business intelligence platform. In the next years, Power BI will continue to be an industry leader in scope. If you enjoy working with data, visualizations, gaining insights, etc., obtaining a Power BI certification could stand you apart in the job market.

What is Power BI?

Power BI is the current buzzword in the data-driven IT business. Numerous power BI potentials exist across several editions. With enough understanding of the equipment, it is simple to seize chances as a:

Power BI data analyst

Power BI consultant

Power BI software engineer

Power BI project manager

Power BI developer

SQL Server Power BI developer

Interview Questions 1. What are Power BI’s most important elements?

Power Pivot: It is used for data modeling that employs DAX (Data Analysis Expression) functions. Here, we can build relationships between many tables and get values that may be shown in pivot tables.

Power View: The Power View presents data intelligibly and gets metadata for data analysis. The views are interactive, and slicers and filters are available for manipulating the data.

Power BI Desktop: Power Desktop is a Power Query, Power View, and Power Pivot integration tool. It facilitates the creation of complex queries, data models, reports, and dashboards, along with developing BI skills for data analysis.

The Power BI Mobile App is available on Android, iOS, and even Windows operating systems. The App has an interactive dashboard display that can be shared.

Power BI Map: It displays geospatial visualization of the data in three-dimensional mode. The data may be highlighted based on geographical location, a continent, state, city, or street address.

Power BI Q&A: It is used to deliver responses to user-posed inquiries. It is compatible with Power View and may be replied with diagrams using Power Q&A.

(Source: InterviewBit)

2. What is Microsoft’s Power BI Gateway?

Power BI Gateway is a software program to access on-premises network data from the cloud. Gateways are gatekeepers for data sources located on-premises. Requests for access to on-premises data from cloud or web-based applications are sent through the gateway. The gateway handles all connection requests and grants access depending on the user’s authentication and criteria.

Gateways do not transmit data from the source on-premises to the client platform. It just links the platform to the on-premises data source so that customers can easily access the data. Gateways have employed a link between a single or several data sources and an on-premises data source.

3. What is the Dax Function used by Power BI?

Data Analysis Expression (DAX) is a formula library for data analysis and computation. This library includes calculation-performing functions, constants, and operators. DAX facilitates the optimal usage of data sets and the generation of meaningful outputs.

DAX is a functional programming language that supports conditional statements, nested functions, value references, and much more. There are either numeric (integers, decimals, etc.) or non-numerical formulae (string, binary). Every DAX formula begins with an equal sign.

DAX Syntax:

Total Sales = SUM(Sales[SalesAmount])

Where ‘Total Sales’ represents ‘Measure,’ ‘SUM’ represents ‘DAX Function,’ and ‘Sales[SalesAmount]’ is the table and column reference.

4. What are Microsoft’s Power BI formats?

The several Power BI formats are as follows:

Power BI Desktop – You may download and install Power BI Desktop on your computer. With templates, you may connect it to the data source, convert the data, and analyze and visualize it.

Power BI Services – Power BI Services is a cloud-based Service-as-a-Platform.

Power BI Mobile App – The Power BI Mobile App is available for iOS, Android, and Windows.

5. What do you mean by the content pack in Power BI?

A content pack is a pre-assembled collection of visualizations, and Power BI reports created with your preferred service. Instead of writing a report from scratch, you would utilize a content pack when you need to start quickly.

6. What visualization types does Power BI support?

Visualization is the rendering of data graphically. Using visualizations, we may generate reports and dashboards. Power BI visualizations include Bar charts, Column charts, Line charts, Area charts, Stacked area charts, Ribbon charts, Waterfall charts, Scatter charts, Pie charts, Donut charts, Treemap charts, Maps, Funnel charts, Gauge charts, Cards, KPI, Slicers, Tables, Matrix, R script visualizations, and Python visualizations, among others.

7. Where does Power BI store data?

When data is imported into Power BI, it is stored primarily in Fact and Dimension tables.

Fact tables: The central table in a star design of a data warehouse, the fact tables hold non-standardized quantitative data for analysis.

Dimension tables: Dimension tables are the only additional table in the star schema used to record characteristics and dimensions that characterize entities in the fact table.

8. What is Power BI’s complete functioning system?

Microsoft’s Power BI system consists mainly of three steps:

Data Integration: Data Integration begins with the extraction and integration of data from disparate data sources. After integration, the data is converted into a standardized format and stored in a staging area.

Data Processing: After the data has been compiled and merged, it must be cleansed before processing. Therefore, a few modifications and cleaning operations are done on the data to remove redundant numbers, etc., as raw data is not very valuable. The modified data is then stored in data warehouses.

Data Presentation: Now that the data has been translated and cleansed, It is shown on the Power BI desktop in the form of reports, dashboards, and scorecards. These reports may be shared with multiple corporate users through mobile apps or the web.

10. What do you understand by Power BI Designer?

Power BI Designer, a powerful and flexible tool under the Power BI umbrella, allows users to build intuitive reports and dashboards easily and swiftly and to modify the visual perspectives of their data on the fly for improved analytics and well-informed decision. This designer is replete with drag-and-drop features that allow users to position content accurately where they want it on the report canvas systematically.

The following are some of Power BI’s limitations:

Complex in nature: Power BI has a fairly sophisticated design. Users must comprehensively understand Power BI before they can begin using it.

Problems with Large Data: Power BI cannot analyze large datasets and may stall out when trying to do so. It is unable to handle files larger than 1 GB.

Limited Sharing of Data: Users who are on the same domain or whose email addresses are designated in Office 365 are the only ones who may get the files you share.

Limited Source of Data: Power BI allows real-time connectivity with a small number of data sources.


Microsoft Power BI is the focus of this article. An analytics system developed by Microsoft, Power BI facilitates the conversion of diverse data sources into relevant and interactive insights. A fast-growing corporate analytics service from the company. Some key takeaways from the article are:

What are Power BI and its important elements?

A complete functioning system of Power BI.

Where does Microsoft’s Power BI store data?

In addition to Power BI Gateway, Power BI Designer, and Power BI Formats, other subjects are also covered.

I hope this Microsoft’s Power BI Interview Questions and Answers help you prepare for your upcoming interviews. Wishing you the best!

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Top 10 Java Interview Questions And Answers

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Cracking an interview for a position using Java can be quite challenging—even though you’re applying for a standard software development job; the SATs appear simple given the variety of questions you might encounter. The purpose of this article is to enlighten you about the kinds of Java interview questions and answers, regardless of their nature. If you have Java on your CV, you could be questioned about everything—from the very first release to the most recent. In essence, how to stay abreast with everything? Let’s find out!

Java Interview Questions and Answers for Freshers

These questions cover critical basic Java principles that will greatly aid your preparation. Hence, the following are the top five Java interview questions and answers for new hires.

1. What are the Main Distinctions between C++ and Java?

C++ and Java are both object-oriented programming languages with some distinctions. The interviewer may inquire about the distinction between the two and add it among the top Java interview questions for freshers to assess their fundamental understanding.

C++ Java

C++ is platform-dependent.

Java is platform-independent.

It creates structured programs without the need for classes or objects.

With the exception of basic variables, Java is a pure object-oriented language.

Pointers are fully supported in C++.

There is no concept of pointers in Java.

C++ allows for multiple inheritances.

Java does not allow for multiple inheritances.

2. What is Thread Priority? 3. Which is Preferred: The Synchronized Method or the Synchronized Block?

The synchronized block is favored because it does not lock the object, whereas synchronized methods do. In fact, if there are several synchronization blocks in the class, even if they are unrelated, it will stop the execution and place them in a wait state to obtain the lock on the object.

4. How to Get the Database Server Details in the Java Program?

We may access the database server details by using the DatabaseMetaData object. When the database connection is properly established, we can retrieve the metadata object by invoking the getMetaData() function. There are also other methods in DatabaseMetaData that may be used to determine the product name, version, and configuration parameters.

DatabaseMetaData metadata = con.getMetaData();

5. What is a Java Object?

In Java, an object is a data structure that represents a physical entity. An object in Java might be a tangible entity like a vehicle or an abstract idea like a mathematical formula. In addition, each object has its own set of information and behavior. Moreover, the object’s data is the information it holds, but its behavior is its capacity to do certain activities.

ALSO READ: How to Become a Game Developer and Create Great Gaming Experiences

Java Interview Questions for Experienced Candidates 6. Can the Keywords “This” and “Super” be Used Together?

No, the terms “this” and “super” should not be used in the initial sentence of the class constructor. 

7. What is Java Session Management?

A session is defined as the dynamic state of random communication between the client and server. The virtual communication channel includes a string of replies and requests from both sides. The most common method of implementing session management is to create a session ID in both the client and server’s communicative discourse.

8. What is JCA in Java?

Java Cryptography Architectural (JCA) provides a framework for decryption and encryption, as well as architecture and application programming interfaces. Additionally. Java Cryptography Architecture is used by developers to integrate the application with security applications. In fact, the Java Cryptography Architecture facilitates the implementation of third-party security rules and regulations. To accomplish security, Java Cryptography Architecture uses hash tables, encryption message digests, etc.

9. What is the Distinction between chúng tôi chúng tôi and

System.out and chúng tôi are the monitor’s default representations and may thus be used to deliver data or results to the monitor. chúng tôi is used to output standard messages and results. Error messages are shown using System.eerr. Moreover, chúng tôi provides an InputStream object which represents a conventional input device, such as a keyboard, by default.

10. Is it Possible to Overload the Main Method?

Yes, we may overload the main method as many times as we like. Nonetheless, the JVM prefers to use its designated calling mechanism to invoke the main function.


ALSO READ: What is Full Stack Development? The Ultimate 2023 Guide

Tips for Java Interview Questions and Answers

Here are a few tips for Java interview questions and answers:

Have a realistic resume

Know the fundamentals of computer science

Expect to be asked to write code on a whiteboard or on paper

Listen carefully to the questions

Be thorough with simple and complex Java principles and concepts

Learning more about the Java programming language is now easier than ever: In fact, Emeritus offers a multitude of online coding courses that could help you ace interviews and bag your dream job.

Write to us at [email protected]

Top 60 Hadoop Interview Questions And Answers (2023)

Here are Hadoop MapReduce interview questions and answers for fresher as well experienced candidates to get their dream job.

Hadoop MapReduce Interview Questions 1) What is Hadoop Map Reduce?

For processing large data sets in parallel across a Hadoop cluster, Hadoop MapReduce framework is used. Data analysis uses a two-step map and reduce process.

2) How Hadoop MapReduce works?

In MapReduce, during the map phase, it counts the words in each document, while in the reduce phase it aggregates the data as per the document spanning the entire collection. During the map phase, the input data is divided into splits for analysis by map tasks running in parallel across Hadoop framework.

👉 Free PDF Download: Hadoop & MapReduce Interview Questions & Answers

3) Explain what is shuffling in MapReduce?

The process by which the system performs the sort and transfers the map outputs to the reducer as inputs is known as the shuffle

4) Explain what is distributed Cache in MapReduce Framework?

Distributed Cache is an important feature provided by the MapReduce framework. When you want to share some files across all nodes in Hadoop Cluster, Distributed Cache is used. The files could be an executable jar files or simple properties file.

5) Explain what is NameNode in Hadoop?

NameNode in Hadoop is the node, where Hadoop stores all the file location information in HDFS (Hadoop Distributed File System). In other words, NameNode is the centerpiece of an HDFS file system. It keeps the record of all the files in the file system and tracks the file data across the cluster or multiple machines

6) Explain what is JobTracker in Hadoop? What are the actions followed by Hadoop?

In Hadoop for submitting and tracking MapReduce jobs, JobTracker is used. Job tracker run on its own JVM process

Job Tracker performs following actions in Hadoop

Client application submit jobs to the job tracker

JobTracker communicates to the Name mode to determine data location

Near the data or with available slots JobTracker locates TaskTracker nodes

On chosen TaskTracker Nodes, it submits the work

When a task fails, Job tracker notifies and decides what to do then.

The TaskTracker nodes are monitored by JobTracker

7) Explain what is heartbeat in HDFS?

Heartbeat is referred to a signal used between a data node and Name node, and between task tracker and job tracker, if the Name node or job tracker does not respond to the signal, then it is considered there is some issues with data node or task tracker

8) Explain what combiners are and when you should use a combiner in a MapReduce Job?

To increase the efficiency of MapReduce Program, Combiners are used. The amount of data can be reduced with the help of combiner’s that need to be transferred across to the reducers. If the operation performed is commutative and associative you can use your reducer code as a combiner. The execution of combiner is not guaranteed in Hadoop

9) What happens when a data node fails?

When a data node fails

Jobtracker and namenode detect the failure

On the failed node all tasks are re-scheduled

Namenode replicates the user’s data to another node

10) Explain what is Speculative Execution?

In Hadoop during Speculative Execution, a certain number of duplicate tasks are launched. On a different slave node, multiple copies of the same map or reduce task can be executed using Speculative Execution. In simple words, if a particular drive is taking a long time to complete a task, Hadoop will create a duplicate task on another disk. A disk that finishes the task first is retained and disks that do not finish first are killed.

11) Explain what are the basic parameters of a Mapper?

The basic parameters of a Mapper are

LongWritable and Text

Text and IntWritable

12) Explain what is the function of MapReduce partitioner?

The function of MapReduce partitioner is to make sure that all the value of a single key goes to the same reducer, eventually which helps even distribution of the map output over the reducers

13) Explain what is a difference between an Input Split and HDFS Block?

The logical division of data is known as Split while a physical division of data is known as HDFS Block

14) Explain what happens in text format?

In text input format, each line in the text file is a record. Value is the content of the line while Key is the byte offset of the line. For instance, Key: longWritable, Value: text

15) Mention what are the main configuration parameters that user need to specify to run MapReduce Job?

The user of the MapReduce framework needs to specify

Job’s input locations in the distributed file system

Job’s output location in the distributed file system

Input format

Output format

Class containing the map function

Class containing the reduce function

JAR file containing the mapper, reducer and driver classes

16) Explain what is WebDAV in Hadoop?

To support editing and updating files WebDAV is a set of extensions to HTTP. On most operating system WebDAV shares can be mounted as filesystems, so it is possible to access HDFS as a standard filesystem by exposing HDFS over WebDAV.

17) Explain what is Sqoop in Hadoop?

To transfer the data between Relational database management (RDBMS) and Hadoop HDFS a tool is used known as Sqoop. Using Sqoop data can be transferred from RDMS like MySQL or Oracle into HDFS as well as exporting data from HDFS file to RDBMS

18) Explain how JobTracker schedules a task?

The task tracker sends out heartbeat messages to Jobtracker usually every few minutes to make sure that JobTracker is active and functioning. The message also informs JobTracker about the number of available slots, so the JobTracker can stay up to date with wherein the cluster work can be delegated

19) Explain what is Sequencefileinputformat?

Sequencefileinputformat is used for reading files in sequence. It is a specific compressed binary file format which is optimized for passing data between the output of one MapReduce job to the input of some other MapReduce job.

20) Explain what does the conf.setMapper Class do?

Conf.setMapperclass sets the mapper class and all the stuff related to map job such as reading data and generating a key-value pair out of the mapper

21) Explain what is Hadoop?

It is an open-source software framework for storing data and running applications on clusters of commodity hardware. It provides enormous processing power and massive storage for any type of data.

22) Mention what is the difference between an RDBMS and Hadoop?

RDBMS Hadoop

RDBMS is a relational database management system Hadoop is a node based flat structure

It used for OLTP processing whereas Hadoop It is currently used for analytical and for BIG DATA processing

In RDBMS, the database cluster uses the same data files stored in a shared storage In Hadoop, the storage data can be stored independently in each processing node.

You need to preprocess data before storing it you don’t need to preprocess data before storing it

23) Mention Hadoop core components?

Hadoop core components include,



24) What is NameNode in Hadoop?

NameNode in Hadoop is where Hadoop stores all the file location information in HDFS. It is the master node on which job tracker runs and consists of metadata.

25) Mention what are the data components used by Hadoop?

Data components used by Hadoop are

26) Mention what is the data storage component used by Hadoop?

The data storage component used by Hadoop is HBase.

27) Mention what are the most common input formats defined in Hadoop?

The most common input formats defined in Hadoop are;




28) In Hadoop what is InputSplit?

It splits input files into chunks and assigns each split to a mapper for processing.

29) For a Hadoop job, how will you write a custom partitioner?

You write a custom partitioner for a Hadoop job, you follow the following path

Create a new class that extends Partitioner Class

Override method getPartition

In the wrapper that runs the MapReduce

Add the custom partitioner to the job by using method set Partitioner Class or – add the custom partitioner to the job as a config file

30) For a job in Hadoop, is it possible to change the number of mappers to be created?

No, it is not possible to change the number of mappers to be created. The number of mappers is determined by the number of input splits.

31) Explain what is a sequence file in Hadoop?

To store binary key/value pairs, sequence file is used. Unlike regular compressed file, sequence file support splitting even when the data inside the file is compressed.

32) When Namenode is down what happens to job tracker?

Namenode is the single point of failure in HDFS so when Namenode is down your cluster will set off.

33) Explain how indexing in HDFS is done?

Hadoop has a unique way of indexing. Once the data is stored as per the block size, the HDFS will keep on storing the last part of the data which say where the next part of the data will be.

34) Explain is it possible to search for files using wildcards?

Yes, it is possible to search for files using wildcards.

35) List out Hadoop’s three configuration files?

The three configuration files are




36) Explain how can you check whether Namenode is working beside using the jps command?

Besides using the jps command, to check whether Namenode are working you can also use

/etc/init.d/hadoop-0.20-namenode status.

37) Explain what is “map” and what is “reducer” in Hadoop?

In Hadoop, a reducer collects the output generated by the mapper, processes it, and creates a final output of its own.

38) In Hadoop, which file controls reporting in Hadoop?

In Hadoop, the file controls reporting.

39) For using Hadoop list the network requirements?

For using Hadoop the list of network requirements are:

Password-less SSH connection

Secure Shell (SSH) for launching server processes

40) Mention what is rack awareness?

Rack awareness is the way in which the namenode determines on how to place blocks based on the rack definitions.

41) Explain what is a Task Tracker in Hadoop?

A Task Tracker in Hadoop is a slave node daemon in the cluster that accepts tasks from a JobTracker. It also sends out the heartbeat messages to the JobTracker, every few minutes, to confirm that the JobTracker is still alive.

42) Mention what daemons run on a master node and slave nodes?

Daemons run on Master node is “NameNode”

Daemons run on each Slave nodes are “Task Tracker” and “Data”

43) Explain how can you debug Hadoop code?

The popular methods for debugging Hadoop code are:

By using web interface provided by Hadoop framework

By using Counters

44) Explain what is storage and compute nodes?

The storage node is the machine or computer where your file system resides to store the processing data

The compute node is the computer or machine where your actual business logic will be executed.

45) Mention what is the use of Context Object?

The Context Object enables the mapper to interact with the rest of the Hadoop

system. It includes configuration data for the job, as well as interfaces which allow it to emit output.

46) Mention what is the next step after Mapper or MapTask?

The next step after Mapper or MapTask is that the output of the Mapper are sorted, and partitions will be created for the output.

47) Mention what is the number of default partitioner in Hadoop?

In Hadoop, the default partitioner is a “Hash” Partitioner.

48) Explain what is the purpose of RecordReader in Hadoop? 49) Explain how is data partitioned before it is sent to the reducer if no custom partitioner is defined in Hadoop?

If no custom partitioner is defined in Hadoop, then a default partitioner computes a hash value for the key and assigns the partition based on the result.

50) Explain what happens when Hadoop spawned 50 tasks for a job and one of the task failed?

It will restart the task again on some other TaskTracker if the task fails more than the defined limit.

51) Mention what is the best way to copy files between HDFS clusters?

The best way to copy files between HDFS clusters is by using multiple nodes and the distcp command, so the workload is shared.

52) Mention what is the difference between HDFS and NAS?

HDFS data blocks are distributed across local drives of all machines in a cluster while NAS data is stored on dedicated hardware.

53) Mention how Hadoop is different from other data processing tools?

In Hadoop, you can increase or decrease the number of mappers without worrying about the volume of data to be processed.

54) Mention what job does the conf class do?

Job conf class separate different jobs running on the same cluster. It does the job level settings such as declaring a job in a real environment.

55) Mention what is the Hadoop MapReduce APIs contract for a key and value class?

For a key and value class, there are two Hadoop MapReduce APIs contract

The value must be defining the interface

The key must be defining the interface

56) Mention what are the three modes in which Hadoop can be run?

The three modes in which Hadoop can be run are

Pseudo distributed mode

Standalone (local) mode

Fully distributed mode

57) Mention what does the text input format do?

The text input format will create a line object that is an hexadecimal number. The value is considered as a whole line text while the key is considered as a line object. The mapper will receive the value as ‘text’ parameter while key as ‘longwriteable’ parameter.

58) Mention how many InputSplits is made by a Hadoop Framework?

Hadoop will make 5 splits

1 split for 64K files

2 split for 65mb files

2 splits for 127mb files

59) Mention what is distributed cache in Hadoop?

Distributed cache in Hadoop is a facility provided by MapReduce framework. At the time of execution of the job, it is used to cache file. The Framework copies the necessary files to the slave node before the execution of any task at that node.

60) Explain how does Hadoop Classpath plays a vital role in stopping or starting in Hadoop daemons?

Classpath will consist of a list of directories containing jar files to stop or start daemons.

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34+ Agile Testing Interview Questions And Answers (2023)

1) As a tester what should be your approach when requirements change continuously?

Following is a list of Agile Testing interview questions and answers, which are likely to be asked during the interview.

When requirement keeps changing, continuously agile tester should take following approach

Write generic test plans and test cases, which focuses on the intent of the requirement rather than its exact details

To understand the scope of change, work closely with the product owners or business analyst

Make sure team understand the risks involved in changing requirements especially at the end of the sprint

Until the feature is stable, and the requirements are finalized, it is best to wait if you are going to automate the feature

Changes can be kept to a minimum by negotiating or implement the changes in the next sprint

2) List out the pros and cons of exploratory testing (used in Agile) and scripted testing?

Pros Cons

Exploratory Testing – It requires less preparation- Easy to modify when requirement changes- Works well when documentation is scarce – Presenting progress and Coverage to project management is difficult

Scripted Testing – In case testing against legal or regulatory requirements it is very useful – Test preparation is usually time-consuming- Same steps are tested over and again- When requirement changes it is difficult to modify

3) Explain the difference between Extreme programming and Scrum?

Scrum Extreme Programing (XP)

– Scrum teams usually have to work in iterations called sprints which usually last up to two weeks to one month long – XP team works in iteration that last for one or two weeks

– Scrum teams do not allow change into their sprints – XP teams are more flexible and change their iterations

– In scrum, the product owner prioritizes the product backlog but the team decides the sequence in which they will develop the backlog items – XP team work in strict priority order, features developed are prioritized by the customer

– Scrum does not prescribe any engineering practices – XP does prescribe engineering practices

4) What is an epic, user stories and task?

Epic: A customer described software feature that is itemized in the product backlog is known as epic. Epics are sub-divided into stories

User Stories: From the client perspective user stories are prepared which defines project or business functions, and it is delivered in a particular sprint as expected.

Task: Further down user stories are broken down into different task

5) Explain what is re-factoring?

To improve the performance, the existing code is modified; this is re-factoring. During re-factoring the code functionality remains same

6) Explain how you can measure the velocity of the sprint with varying team capacity?

When planning a sprint usually, the velocity of the sprint is measured on the basis of professional judgement based on historical data. However, the mathematical formula used to measure the velocity of the sprint are,

first – completed story points X team capacity: If you measure capacity as a percentage of a 40 hours weeks

Second – completed story points / team capacity: If you measure capacity in man-hours

For our scenario second method is applicable.

7) Mention the key difference between sprint backlog and product backlog?

Product backlog: It contains a list of all desired features and is owned by the product owner.

Sprint backlog: It is a subset of the product backlog owned by development team and commits to deliver it in a sprint. It is created in Sprint Planning Meeting

8) In Agile mention what is the difference between the Incremental and Iterative development?

Iterative: Iterative method is a continuous process of software development where the software development cycles are repeated (Sprint & Releases) till the final product is achieved.

Release 1: Sprint 1, 2… n

Release n: Sprint 1, 2….n

9) Explain what is Spike and Zero sprint in Agile? What is the purpose of it?

Sprint Zero: It is introduced to perform some research before initiating the first sprint. Usually this sprint is used during the start of the project for activities like setting development environment, preparing product backlog and so on.

Spikes: Spikes are type of stories that are used for activities like research, exploration, design and even prototyping. In between sprints, you can take spikes for the work related to any technical or design issue. Spikes are of two types Technical Spikes and Functional Spikes.

10) What is test driven development?

Test driven development or TDD is also known as test-driven design. In this method, developer first writes an automated test case which describes new function or improvement and then creates small codes to pass that test, and later re-factors the new code to meet the acceptable standards.

11) Prototypes and Wireframes are widely used as part of?

Prototypes and Wireframes are prototypes that are widely used as part of Empirical Design.

12) Explain what is Application Binary Interface?

Across different system platforms and environments a specification defining requirements for portability of applications in binary form is known as Application Binary Interface.

13) Explain in Agile, burn-up and burn-down chart?

To track the project progress burnup and burn down, charts are used.

Burnup Chart: It shows the progress of stories done over time.

Burndown Chart: It shows how much work was left to do overtime.

14) Explain what is Scrum ban?

Scrum ban is a software development model based on Scrum and Kanban. It is specially designed for project that requires frequent maintenance, having unexpected user stories and programming errors. Using these approach, the team’s workflow is guided in a way that allows minimum completion time for each user story or programming error.

15) What is story points/efforts/ scales?

16) Explain what is tracer bullet?

The tracer bullet is a spike with the current architecture, the current set of best practices, current technology set which results in production quality code. It is not a throw away code but might just be a narrow implementation of the functionality.

17) What is a test stub?

A test stub is a small code that replaces an undeveloped or fully developed component within a system being tested. Test stub is designed in such a way that it mimics the actual component by generating specifically known outputs and substitute the actual component.

18) What are the differences between RUP (Rational Unified Process) and Scrum methodologies?


– Formal Cycle is defined across four phases, but some workflows can be concurrent – Each sprint is a complete cycle

– Formal project plan, associated with multiple iterations is used. – No end to end project plan. Each next iteration plan is determined at the end of the current iteration

– Scope is predefined ahead of the project start and documented in the scope document. During the project, scope can be revised. – It uses a project backlog instead of scope scrum

– Artifacts include Scope Document, formal functional requirements package, system architecture document, development plan, test scripts, etc. – Operational software is the only formal artifacts

– Recommended for long term, large, enterprise level projects with medium to high complexity – Recommended for quick enhancements and organization that are not dependent on a deadline

19) Why Continuous Integration is important for Agile?

Continuous Integration is important for Agile for following reasons.

It helps to maintain release schedule on time by detecting bugs or integration errors

Due to frequent agile code delivery usually every sprint of 2-3 weeks, stable quality of build is a must and continuous integration ensures that

In helps to maintain the quality and bug free state of code-base

Continuous integration helps to check the impact of work on branches to the main trunk if development work is going on branches using automatic building and merging function

20) What testing is done during Agile?

The primary testing activities during Agile is automated unit testing and exploratory testing.

Though, depending on project requirements, a tester may execute Functional and Non-functional tests on the Application Under Test (AUT).

21) Explain what is Velocity in Agile?

Velocity is a metric that is calculated by addition of all efforts estimates related with user stories completed in an iteration. It figures out how much work Agile can complete in a sprint and how much time will it need to finish a project.

22) What are the qualities of a good Agile tester should have?

A good Agile tester should have following qualities

It should be able to understand the requirements quickly

Agile tester should know Agile principals and concepts well

As requirements keep changing, tester should understand the risk involve in it

Based on the requirements Agile tester should be able to prioritize the work

Continue communication between business associates, developers and tester is must

23) Who are all involved in the Agile team?

Scrum Masters: It coordinates most of the inputs and outputs required for an agile program

Development Managers: They hire right people and develop them with the team

24) Mention in detail what are the role’s of Scrum Master?

Scrum Master key responsibilities involves

Understand the requirements and turn them into working software

Monitoring and Tracking

Reporting and Communication

Process Check Master

Quality Master

Resolve Impediments

Resolve Conflicts

Shield the team and performance feedback

Lead all the meetings and resolve obstacles

25) Mention what are the Agile quality strategies?

Agile quality strategies are


Non-solo development

Static and dynamic code analysis

Reviews and Inspection

Iteration/sprint demos

All hands demo

Light weight milestone reviews

Short feedback cycles

Standards and guidelines

26) Mention what are the Tools that can be useful for screenshots while working on Agile projects?

While working on Agile projects you can use tools like







It helps team to objectively measure progress

It provides a consistent means of measuring team velocity

It helps to establish a consistent pattern of delivery

28) If a timebox plan needs to be reprioritized who should re-prioritise it?

If a timebox plan needs to be reprioritized it should include whole team, product owner, and developers.

29) Mention what should a burndown chart should highlight?

The burn-down chart shows the remaining work to complete before the timebox (iteration) ends.

30) Mention what is the difference between Scrum and Agile?

Scrum: In the scrum, a sprint is a basic unit of development. Each sprint is followed by a planning meeting, where the tasks for the sprint are identified and estimated. During each sprint, the team creates finished portion of a product

Agile: In Agile, each iteration involves a team working through a full software development cycle, including planning, design, coding, requirement analysis, unit testing, and acceptance testing when a product is demonstrated to stakeholders

In simple words, Agile is the practice and scrum is the process to following this practice.

31) Mention what are the challenges involved in AGILE software development?

Challenges involved in Agile Software development includes

It requires more testing and customers involvement

It impacts management more than developers

Each feature needs to be completed before moving on to the next

All the code has to work fine to ensure application is in working state

More planning is required

32) When not to use Agile?

Before using Agile methodology, you must ask following questions

Is functionality split-able

Is customer available

Are requirements flexible

Is it really time constrained

Is team skilled enough

33) Explain how can you implement scrum in an easy way to your project?

These are the tips which can be helpful to implement scrum in your project.

Get your backlog in order

Get an idea of the size of your product backlog items

Clarify sprint requirement and duration to complete the sprint backlog

Calculate the team sprint budget and then break requirements into tasks

Collaborate workspace- a center of all team discussion, which includes plans, roadmaps, key dates, sketches of functionality, issues, log, status reports, etc.

Sprint- Make sure you complete one feature at a time before moving on to the next. A sprint should not be abort unless if there is no other option

Attend a daily stand-up meeting: In meeting you need to mention, what have been achieved since the last meeting, what will they achieve before the next meeting and is anything holding up their progress

Use burndown chart to track daily progress. From the burndown chart, you can estimate whether you are on track, or you are running behind

Complete each features well before moving on to the next

At the end of the sprint- hold a sprint review meeting, mention what is achieved or delivered in the sprint.

34) Explain what does it mean by product roadmap?

A product roadmap is referred for the holistic view of product features that create the product vision.

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Top 18 R Programming Interview Questions & Answers (2023)

Here are R Programming interview questions and answers for fresher as well experienced candidates to get their dream job.

1) Explain what is R?

R is data analysis software which is used by analysts, quants, statisticians, data scientists and others.

2) List out some of the function that R provides?

The function that R provides are







Mixed Effects


GAM. etc.

3) Explain how you can start the R commander GUI?

Typing the command, (“Rcmdr”) into the R console starts the R commander GUI.

4) In R how you can import Data?

You use R commander to import Data in R, and there are three ways through which you can enter data into it

You can enter data directly via Data  New Data Set

Import data from a plain text (ASCII) or other files (SPSS, Minitab, etc.)

Read a data set either by typing the name of the data set or selecting the data set in the dialog box

5) Mention what does not ‘R’ language do?

Though R programming can easily connects to DBMS is not a database

R does not consist of any graphical user interface

6) Explain how R commands are written?

In R, anywhere in the program you have to preface the line of code with a #sign, for example

# subtraction

# division

# note order of operations exists

7) How can you save your data in R?

To save data in R, there are many ways, but the easiest way of doing this is

8) Mention how you can produce co-relations and covariances?

You can produce co-relations by the cor () function to produce co-relations and cov () function to produce covariances.

9) Explain what is t-tests in R?

10) Explain what is With () and By () function in R is used for?

With() function is similar to DATA in SAS, it apply an expression to a dataset.

BY() function applies a function to each level of factors. It is similar to BY processing in SAS.

11) What are the data structures in R that is used to perform statistical analyses and create graphs?

R has data structures like




Data frames

12) Explain general format of Matrices in R?

General format is

Mymatrix< - matrix (vector, nrow=r , ncol=c , byrow=FALSE, dimnames = list ( char_vector_ rowname, char_vector_colnames)) 13) In R how missing values are represented ?

In R missing values are represented by NA (Not Available), why impossible values are represented by the symbol NaN (not a number).

14) Explain what is transpose?

15) Explain how data is aggregated in R?

By collapsing data in R by using one or more BY variables, it becomes easy. When using the aggregate() function the BY variable should be in the list.

16) What is the function used for adding datasets in R?

rbind function can be used to join two data frames (datasets). The two data frames must have the same variables, but they do not have to be in the same order.

17) What is the use of subset() function and sample() function in R ?

In R, subset() functions help you to select variables and observations while through sample() function you can choose a random sample of size n from a dataset.

18) Explain how you can create a table in R without external file?

Use the code

myTable = data.frame() edit(myTable)

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