EPAM Systems Interview Questions, Process, and Tips

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Q1. Front End Technologies html css js
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Q1. How to make class mutable?
Ans. 
To make a class mutable, provide public setter methods to modify its internal state.
• Add public setter methods to modify class fields

• Avoid using final keyword for class fields

• Implement proper validation logic in setter methods

• Consider thread safety when allowing mutability
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Q2. In array smallest product elements
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Find the smallest product of elements in an array of strings.
• Convert each string element to integer and calculate the product of all elements.

• Keep track of the smallest product found so far.

• Return the smallest product at the end.
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Q3. How to design for input and output files?
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Designing for input and output files involves considering file formats, data validation, error handling, and security measures.
• Understand the requirements for input and output files, including file formats and data structures.

• Implement data validation to ensure that input files meet the required format and content.

• Include error handling mechanisms to address issues such as missing files or incorrect data.

• Consider secur...read more
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Q1. Java basics + 2 qs on dsa
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Q1. Java + dsa , java design patterns
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Q1. Design YouTube, some questions on linked list and trees
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Q1. TEst strategy document
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Q2. Finally vs finalize
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finally is used in exception handling to define a block of code that will always be executed, while finalize is a method in Java used for cleanup operations before an object is destroyed.
• finally is used in try-catch blocks to define a block of code that will always be executed, regardless of whether an exception is thrown or not

• finalize is a method in Java that is called by the garbage collector before an object is des...read more
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Q3. 403 status code meaning
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403 status code means forbidden access to the requested resource.
• 403 status code indicates that the server understood the request but refuses to authorize it.

• It is commonly used when the user does not have the necessary permissions to access the resource.

• Examples include trying to access a restricted page without proper credentials or attempting to perform an action that requires higher privileges.
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Q4. Test listeners types
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Test listeners types are used in software testing to monitor and respond to events during test execution.
• Types of test listeners include TestNG listeners, JUnit listeners, and custom listeners

• TestNG listeners include ITestListener, ISuiteListener, and IInvokedMethodListener

• JUnit listeners include RunListener and TestWatcher

• Custom listeners can be created to handle specific events in test execution
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Q5. Automation framework
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Q1. Lineage graph,rdd,python decorators,python dict problem,sql self join probelm
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Q2. Types of transformations,no of jobs,tasks,actions
Ans. 
The question is asking about types of transformations, number of jobs, tasks, and actions in the context of a Senior Data Engineer role.
• Types of transformations: Extract, Transform, Load (ETL), MapReduce, Spark transformations, SQL transformations

• Number of jobs: Depends on the complexity and scale of the data engineering projects

• Number of tasks: Varies based on the number of data sources, data transformations, and data...read more
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Q3. Fact,dimesnion,star and snowflake schema
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Q4. Architecture of spark,airflow,bigquery,
Ans. 
Spark is a distributed processing engine, Airflow is a workflow management system, and BigQuery is a fully managed data warehouse.
• Spark is designed for big data processing and provides in-memory computation capabilities.

• Airflow is used for orchestrating and scheduling data pipelines.

• BigQuery is a serverless data warehouse that allows for fast and scalable analytics.

• Spark can be integrated with Airflow to schedule and m...read more
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Q5. Optimisation in spark,sql,bigquery,airflow
Ans. 
Optimization techniques in Spark, SQL, BigQuery, and Airflow.
• Use partitioning and bucketing in Spark to optimize data processing.

• Optimize SQL queries by using indexes, query rewriting, and query optimization techniques.

• In BigQuery, use partitioning and clustering to improve query performance.

• Leverage Airflow's task parallelism and resource allocation to optimize workflow execution.
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Q6. Delete duplicates from table in spark and sql
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To delete duplicates from a table in Spark and SQL, you can use the DISTINCT keyword or the dropDuplicates() function.
• In SQL, you can use the DISTINCT keyword in a SELECT statement to retrieve unique rows from a table.

• In Spark, you can use the dropDuplicates() function on a DataFrame to remove duplicate rows.

• Both methods compare all columns by default, but you can specify specific columns to consider for duplicates.

• You...read more
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Q7. Coaelesce,repartition,shuffling,CDC,acid properties,CDC types
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Q1. Dataflow vs Dataproc, layering processing and curated environments in gcp , Data cleaning
Ans. 
Dataflow and Dataproc are both processing services in GCP, but with different approaches and use cases.
• Dataflow is a fully managed service for executing batch and streaming data processing pipelines.

• Dataproc is a managed Spark and Hadoop service for running big data processing and analytics workloads.

• Dataflow provides a serverless and auto-scaling environment, while Dataproc offers more control and flexibility.

• Dataflow...read more
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Q1. Pyspark field delimited questions with group by transformations, Sql window function question Discussion on arch of spark,bq,airflow. How to define dependency between tasks and two diff dags. star and sno...read more
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This was final round with Client.
They ask questions based on my work in pyspark area.
Questions are like:
What kind of transformations you used.
Broadcast join internals.
Spark internal joins
Spark catalyst optimizer.What are the joins happens in catalyst optimizer.
Window function question: 3rd highest salary of an emp
Discussion on airflow arch and how to deploy a airflow dag in gcp.
Discussion on BQ on what kind of work i have done till now.

Went well and was good

Went well and was good

Q1. Reverse a string
Ans. 
A function to reverse a given string and return it.
• Create an empty string to store the reversed string

• Iterate through the original string from end to start and append each character to the new string

• Return the reversed string
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