In this blog post, i am going to cover most frequently asked Apache Spark Interview Questions. Hope it will help you. 1. What is the difference between map() and flatmap() in Apache Spark? Ans : This is one of the most frequently asked Interview Questions for Spark Developers. For answer this one Question, first i will explain similarities between these two and then we will see the differences between these two. Similarities: Similarity between map() and flatmap() is they take a input line from input RDD and and apply a function on it. Differences: map transforms an RDD of length N into another RDD of length N. But flatMap transforms an RDD of length N into a collection of N collections, then flattens these into a single RDD of results. Example: Here is my input RDD called, input: val input = sc . parallelize ( Seq ( "this is spark blogpost" , "regarding spark interview questions" )) map(): input . map ( _ . length ). collect ...