HCLTech

Global IT services and consulting company.

4 Rounds ~21 Days Medium

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The Interview Loop

Recruiter Screen (30 min)

Standard fit check, behavioral questions, and resume overview.

Technical Loop (3-4 Rounds)

Deep dive into domain knowledge, coding, and system design.

Interview Question Bank

All Roles Data Engineer 9

All Topics System Design 32 Algorithms 27 Culture Fit 20 SQL 17 Deep Learning 11 Machine Learning 10 JavaScript 10 Machine Learning Theory 10

Data Engineer • Coding • medium

Write PySpark code to explode an array column into multiple rows.

#PySpark #DataFrames #Functions

Practice

Data Engineer • Coding • easy

Write a PySpark script to read a massive CSV file, filter out rows with null values in a specific column, group by another column to find the count, and write the output to Parquet format.

#PySpark #DataFrames #I/O

Practice

Data Engineer • Technical • hard

How does Apache Spark handle memory management? Explain the difference between execution memory and storage memory.

#PySpark #Memory Management #Spark Architecture

Practice

Data Engineer • Technical • medium

Explain Broadcast Hash Join vs. Sort Merge Join in Spark. When would you use a Broadcast Join?

#PySpark #Joins #Optimization

Practice

Data Engineer • Technical • hard

You are running a PySpark job that is taking unusually long and you notice that one task is taking 90% of the time while others finish quickly. What is the issue and how do you fix it?

#PySpark #Data Skewness #Performance Tuning

Practice

Data Engineer • Technical • easy

What is the difference between repartition() and coalesce() in PySpark? When should you use each?

#PySpark #Partitions #Shuffling

Practice

Data Engineer • Technical • easy

Explain the concept of lazy evaluation in Spark. What are its benefits?

#PySpark #Spark Architecture #DAG

Practice

Data Engineer • Technical • easy

What is the difference between an external table and a managed table in Hive or Databricks?

#Hive #Databricks #Data Storage

Practice

Data Engineer • Technical • hard

How do you troubleshoot and resolve an OutOfMemory (OOM) error in a PySpark application?

#PySpark #Debugging #Memory Management

Practice

Difficulty Radar

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Meet Your Interviewers

The "Standard" Interviewer

Senior Engineer

Focuses on core competencies, system constraints, and clear communication.

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Unwritten Rules

Think Out Loud

Always explain your thought process before writing code or drawing architecture.

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