HCLTech

Global IT services and consulting company.

4 Rounds ~21 Days Medium

Start Mock Interview

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 Backend Engineer 35 Data Engineer 35 Data Scientist 35 DevOps Engineer 35 Frontend Engineer 35 Full Stack Engineer 35 Machine Learning Engineer 35 Product Manager 35

All Topics Big Data 9 SQL 6 Cloud 5 Culture Fit 4 Algorithms 4 System Design 4 Data Warehousing 2 Leadership 1

Data Engineer • Behavioral • hard

Describe a time you migrated an on-premise Hadoop workload to a cloud environment (AWS/Azure/GCP). What were the major challenges?

#Cloud Migration #Hadoop #Problem Solving

Practice

Data Engineer • Behavioral • medium

Tell me about a time you had to deliver a critical data pipeline under a very tight deadline for a client. How did you manage it?

#Time Management #Client Delivery #Prioritization

Practice

Data Engineer • Behavioral • medium

HCLTech strongly values 'Ideapreneurship'. Can you share an instance where you proactively proposed a technical solution that saved costs or improved pipeline performance?

#Innovation #Cost Optimization #Proactivity

Practice

Data Engineer • Behavioral • hard

Describe a situation where you disagreed with a senior architect or a client regarding a data architecture choice. How did you resolve the conflict?

#Conflict Resolution #Communication #Stakeholder Management

Practice

Data Engineer • Behavioral • medium

How do you ensure data quality, validation, and governance in the pipelines you build?

#Data Quality #Governance #Best Practices

Practice

Data Engineer • Behavioral • easy

Tell me about a time you had to learn a new big data technology or cloud service on the fly to complete a project. How did you approach it?

#Adaptability #Continuous Learning

Practice

Data Engineer • Coding • medium

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

#PySpark #DataFrames #Functions

Practice

Data Engineer • Coding • medium

Write a SQL query to find the nth highest salary from an Employee table without using the LIMIT or TOP keywords.

#Window Functions #Subqueries #SQL Server

Practice

Data Engineer • Coding • medium

Write a SQL query to calculate the cumulative sum of sales per region over time.

#Window Functions #Aggregation #Time Series

Practice

Data Engineer • Coding • easy

Given an Employee table with columns Id, Name, Salary, and ManagerId, write a query to find all employees who earn more than their direct managers.

#Self Joins #Filtering

Practice

Data Engineer • Coding • medium

Write a query to find the 7-day moving average of sales for a retail client.

#Window Functions #Moving Averages #Data Analysis

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 • Coding • easy

Write a Python function to check if a given string is a valid palindrome, ignoring special characters and case.

#Python #Strings #Two Pointers

Practice

Data Engineer • Coding • medium

Write a Python generator function to read a massive 50GB log file line by line without loading the entire file into memory.

#Python #Generators #File I/O

Practice

Data Engineer • Coding • medium

Given a complex nested JSON object (represented as a Python dictionary), write a recursive Python function to flatten it into a single-level dictionary.

#Python #Recursion #JSON

Practice

Data Engineer • Coding • easy

Write a Python function to find the first non-repeating character in a string. Return its index or -1 if it doesn't exist.

#Python #Hash Maps #Strings

Practice

Data Engineer • System Design • hard

Design a real-time streaming pipeline to process IoT sensor data, detect anomalies, and store the results for dashboarding.

#Streaming #Kafka #Spark Streaming #NoSQL

Practice

Data Engineer • System Design • hard

Design a batch processing system to ingest 5TB of application log data daily, clean it, and make it available for reporting.

#Batch Processing #Data Lake #ETL

Practice

Data Engineer • System Design • hard

How would you design the data model for a data warehouse supporting an e-commerce platform's sales analytics?

#Data Modeling #Star Schema #E-commerce

Practice

Data Engineer • System Design • hard

Design a fault-tolerant data ingestion pipeline using Apache Kafka. How do you ensure exactly-once processing?

#Kafka #Fault Tolerance #Exactly-once Semantics

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 • hard

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

#PySpark #Debugging #Memory Management

Practice

Data Engineer • Technical • easy

Explain the exact differences between RANK(), DENSE_RANK(), and ROW_NUMBER() in SQL. Provide a scenario where you would choose DENSE_RANK() over RANK().

#Window Functions #Ranking

Practice

Data Engineer • Technical • hard

You have a slow-running query in Snowflake with multiple joins and a subquery that processes millions of rows. How do you approach optimizing it?

#Query Optimization #Execution Plan #Snowflake

Practice

Data Engineer • Technical • medium

How do you implement a Slowly Changing Dimension (SCD) Type 2 in a data warehouse using SQL or PySpark?

#SCD #Dimensional Modeling #ETL

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 • medium

In Azure Data Factory (ADF), how do you pass parameters dynamically between different activities in a pipeline?

#Azure Data Factory #Pipelines #Dynamic Content

Practice

Data Engineer • Technical • medium

Explain the Medallion Architecture (Bronze, Silver, Gold layers) in Databricks Delta Lake. What is the purpose of each layer?

#Databricks #Delta Lake #Data Architecture

Practice

Data Engineer • Technical • medium

How do you schedule, monitor, and handle dependencies for a complex data pipeline in Apache Airflow?

#Apache Airflow #Orchestration #DAGs

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 • medium

How do you implement an incremental data load (Delta load) using AWS Glue or Azure Data Factory?

#ETL #Incremental Loading #AWS Glue #ADF

Practice

Data Engineer • Technical • medium

Explain the concept of Time Travel in Snowflake or Delta Lake. How is it useful for a Data Engineer?

#Snowflake #Delta Lake #Data Recovery

Practice

Difficulty Radar

Based on recent AI-sourced data.

Meet Your Interviewers

The "Standard" Interviewer

Senior Engineer

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

Simulate

Unwritten Rules

Think Out Loud

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

Practice Now