A must-know for anyone heading into a Spark interview, this question is frequently asked in Spark interview.   Executors are worker nodes' processes in charge of running individual tasks when Spark jobs get submitted. They are launched at the beginning of a Spark application and typically run for the entire lifetime of an application. Once they have run the task, they send the results to the driver. They also provide in-memory storage for RDDs that are cached by user programs through Block Manager. Below are the key points on executors: Every spark application has its own executor process. The executor performs all the data processing. Reads from and Writes data to external sources. The executor stores the computation results in data in-memory, cache, or on hard disk drives. The executor also works as a distributed agent responsible for the execution of tasks. When the job gets launched, the spark triggers the executor, which acts as a worker node responsible for running an individual task which is assigned by spark driver.