eClerx Data Engineer Interview Questions and Answers

Apache Spark architecture includes a cluster manager, worker nodes, and driver program.

• Apache Spark architecture consists of a cluster manager, which allocates resources and schedules tasks.

• Worker nodes execute tasks and store data in memory or disk.

• Driver program coordinates tasks and communicates with the cluster manager.

• Spark applications run as independent sets of processes on a cluster, coordinated by the SparkCon...read more

reduceBy is used to aggregate data based on key, while groupBy is used to group data based on key.

• reduceBy is a transformation that combines the values of each key using an associative function and a neutral 'zero value'.

• groupBy is a transformation that groups the data based on a key and returns a grouped data set.

• reduceBy is more efficient for aggregating data as it reduces the data before shuffling, while groupBy shu...read more

RDD is a low-level abstraction representing a distributed collection of objects, while DataFrame is a higher-level abstraction representing a distributed collection of data organized into named columns.

• RDD is more suitable for unstructured data and low-level transformations, while DataFrame is more suitable for structured data and high-level abstractions.

• DataFrames provide optimizations like query optimization and code...read more

The different modes of execution in Apache Spark include local mode, standalone mode, YARN mode, and Mesos mode.

• Local mode: Spark runs on a single machine with one executor.

• Standalone mode: Spark runs on a cluster managed by a standalone cluster manager.

• YARN mode: Spark runs on a Hadoop cluster using YARN as the resource manager.

• Mesos mode: Spark runs on a Mesos cluster with Mesos as the resource manager.

Use regular expression to remove special characters from a string

• Use the regex pattern [^a-zA-Z0-9\s] to match any character that is not a letter, digit, or whitespace

• Use the replace() function in your programming language to replace the matched special characters with an empty string

• Example: input string 'Hello! How are you?' will become 'Hello How are you' after removing special characters

Databricks is a unified analytics platform that provides a collaborative environment for data scientists, engineers, and analysts.

• Databricks is built on top of Apache Spark, providing a unified platform for data engineering, data science, and business analytics.

• Internals of Databricks include a cluster manager, job scheduler, and workspace for collaboration.

• Optimization techniques in Databricks include query optimizati...read more

Use SQL query to find the product with the second highest total price.

• Use the ORDER BY clause to sort the products by total price in descending order

• Use the LIMIT clause to select the second row after sorting