Top 20 Hadoop MapReduce Interview Questions

BigData and Data analytics Jobs are the most sought after jobs of current time. It is important to understand the basics before you appear for interview. In this post, I am covering few of the basic MapReduce interview questions for Hadoop MapReduce.


  1. What is MapReduce ?

  2. What is combiner and when you should use combiner in MapReduce Job?

  3. What is speculative execution?

  4. What does partitioner do in MapReduce?

  5. What is  the difference between  an InputSplit and HDFS Block?

  6. What is the configuration to run a MapReduce Job ?

  7. What is SequenceFileInputFormat and when we should use it?

  8. What parameters does a Mapper take ?

  9. What parameters does a Reducer take?

  10. What is distributed cache and where it is used?

  11. What is the default InputFormat in MapReduce ? and How does it work?

  12. What is InputSplit in Hadoop MapReduce ?

  13. What is RecordReader and how it is used ?

  14. What is the command to see all current running Jobs in cluster ?

  15. What is the command to kill a particular Job in cluster ?

  16. How can we write output from a MapReduce job to multiple directories ?

  17. How can we set the number of reducers for a MapReduce Job?

  18. How can we debug the MapReduce code ?

  19. What are they types of Schedulers in MapReduce ?

  20. What is Hadoop Streaming?

If you want to refer to some Hadoop Books , please read it here –

Top 20 Hadoop and BigData Books

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