Persistent Systems Interview Questions, Process, and Tips

Business Analyst (BA) focuses on understanding business needs and requirements, while Product Owner (PO) focuses on defining and prioritizing product features.

• BA analyzes business processes and systems to identify areas for improvement, while PO works closely with stakeholders to define product features and prioritize the product backlog.

• BA typically works on multiple projects simultaneously, while PO is dedicated to a...read more

A Java program to find and replace specified characters with corresponding numbers in an array of strings.

• Iterate through each string in the array

• Count the occurrences of specified characters

• Replace the characters with corresponding numbers

• Return the modified array of strings

Separate even and odd numbers in an array, placing even numbers on the right side and odd numbers on the left side.

• Iterate through the array and check if each element is even or odd.

• Create two separate arrays to store even and odd numbers.

• Append even numbers to one array and odd numbers to another.

• Finally, combine the two arrays with even numbers on the right and odd numbers on the left.

I am a Senior Data Engineer with experience in developing data pipelines and optimizing data storage for various projects.

• Developed data pipelines using Apache Spark for real-time data processing

• Optimized data storage using technologies like Hadoop and AWS S3

• Worked on a project to analyze customer behavior and improve marketing strategies

My day-to-day job in the project involved designing and implementing data pipelines, optimizing data workflows, and collaborating with cross-functional teams.

• Designing and implementing data pipelines to extract, transform, and load data from various sources

• Optimizing data workflows to improve efficiency and performance

• Collaborating with cross-functional teams including data scientists, analysts, and business stakeholde...read more

DAGs handle fault tolerance by rerunning failed tasks and maintaining task dependencies.

• DAGs rerun failed tasks automatically to ensure completion.

• DAGs maintain task dependencies to ensure proper sequencing.

• DAGs can be configured to retry failed tasks a certain number of times before marking them as failed.

Shuffling is the process of redistributing data across partitions in a distributed computing environment.

• Shuffling is necessary when data needs to be grouped or aggregated across different partitions.

• It can be handled efficiently by minimizing the amount of data being shuffled and optimizing the partitioning strategy.

• Techniques like partitioning, combiners, and reducers can help reduce the amount of shuffling in MapRed

Repartition increases or decreases the number of partitions in a DataFrame, while Coalesce only decreases the number of partitions.

• Repartition can increase or decrease the number of partitions in a DataFrame, leading to a shuffle of data across the cluster.

• Coalesce only decreases the number of partitions in a DataFrame without performing a full shuffle, making it more efficient than repartition.

• Repartition is typically...read more

Incremental data is handled by identifying new data since the last update and merging it with existing data.

• Identify new data since last update

• Merge new data with existing data

• Update data warehouse or database with incremental changes

SCD stands for Slowly Changing Dimension, a concept in data warehousing to track changes in data over time.

• SCD is used to maintain historical data in a data warehouse.

• There are three types of SCD - Type 1, Type 2, and Type 3.

• Type 1 SCD overwrites old data with new data.

• Type 2 SCD creates a new record for each change, preserving history.

• Type 3 SCD maintains both old and new values in the same record.

• SCD is important for...read more

Reverse a string using SQL and Python codes.

• In SQL, use the REVERSE function to reverse a string.

• In Python, use slicing with a step of -1 to reverse a string.

Use Spark and SQL to find the top 5 countries with the highest population.

• Use Spark to load the data and perform data processing.

• Use SQL queries to group by country and sum the population.

• Order the results in descending order and limit to top 5.

• Example: SELECT country, SUM(population) AS total_population FROM table_name GROUP BY country ORDER BY total_population DESC LIMIT 5

To find different records for different joins using two tables

• Use the SQL query to perform different joins like INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• Identify the key columns in both tables to join on

• Select the columns from both tables and use WHERE clause to filter out the different records

A catalyst optimizer is a query optimization tool used in Apache Spark to improve performance by generating an optimal query plan.

• Catalyst optimizer is a rule-based query optimization framework in Apache Spark.

• It leverages rules to transform the logical query plan into a more optimized physical plan.

• The optimizer applies various optimization techniques like predicate pushdown, constant folding, and join reordering.

• By o...read more

Used query optimization techniques to improve performance in database queries.

• Utilized indexing to speed up search queries.

• Implemented query caching to reduce redundant database calls.

• Optimized SQL queries by restructuring joins and subqueries.

• Utilized database partitioning to improve query performance.

• Used query profiling tools to identify and optimize slow queries.

Use the len() function to check the length of the data frame.

• Use len() function to get the number of rows in the data frame.

• If the length is 0, then the data frame is empty.

• Example: if len(df) == 0: print('Data frame is empty')

Cores and worker nodes are decided based on the workload requirements and scalability needs of the data processing system.

• Consider the size and complexity of the data being processed

• Evaluate the processing speed and memory requirements of the tasks

• Take into account the parallelism and concurrency needed for efficient data processing

• Monitor the system performance and adjust cores and worker nodes as needed

Enforcing schema ensures that data conforms to a predefined structure and rules.

• Ensures data integrity by validating incoming data against predefined schema

• Helps in maintaining consistency and accuracy of data

• Prevents data corruption and errors in data processing

• Can lead to rejection of data that does not adhere to the schema

Terraform daily tasks involve infrastructure provisioning, configuration management, and automation.

• Creating and managing infrastructure using Terraform scripts

• Updating and modifying existing infrastructure as needed

• Automating deployment processes for applications

• Implementing version control for Terraform configurations

• Monitoring and troubleshooting Terraform deployments

RPA stands for Robotic Process Automation, which involves using software robots to automate repetitive tasks.

• RPA uses software robots to automate repetitive tasks, mimicking human actions.

• It can be used to streamline business processes, increase efficiency, and reduce human error.

• RPA tools can interact with existing applications, extract data, and perform tasks across multiple systems.

• Examples of RPA tools include UiPa

RE-Framework is a Robotic Enterprise Framework for automating business processes using UiPath.

• RE-Framework is a template designed by UiPath for building scalable and efficient automation projects.

• It includes pre-built workflows for exception handling, logging, and reusability of components.

• RE-Framework follows a state machine design pattern to manage the flow of automation.

• It allows for easy integration of new processe

Object-oriented programming concepts that focus on data encapsulation, inheritance, polymorphism, and abstraction.

• Encapsulation: Bundling data and methods that operate on the data into a single unit (class).

• Inheritance: Ability of a class to inherit properties and behavior from another class.

• Polymorphism: Ability to present the same interface for different data types.

• Abstraction: Hiding the complex implementation detai...read more

super is used to refer immediate parent class instance variable or method, while this is used to refer current class instance variable or method.

• super is used to access parent class members, while this is used to access current class members

• super keyword is used to invoke parent class constructor, while this keyword is used to invoke current class constructor

• super keyword is used to differentiate between parent and chi...read more