Top PySpark Interview Questions and Answers for 2025

PySpark Interview Questions and Answers (General)

A strong foundation makes a great building. We will take you on this PySpark interview questions journey step by step. Let's start with the basics!

1. What is PySpark?

PySpark = Python + Spark.

You must have seen auditorium lights, but the man behind the scenes is the light controller. In PySpark, Spark is the auditorium lights, and you are the controller. Your role is to write code similar to the light controller, and Spark executes it for you. Spark handles big data, distributes processing, and speeds up computation. PySpark is simply Spark executed with Python.

2. What are RDDs in PySpark?

RDD (Resilient Distributed Datasets) are data structures that allows data processing across all the nodes in a cluster. This is called parallel processing.

Immutable: Once created, it cannot be changed.

Fault-tolerant: the failed RDDs can be automatically recovered.

Efficient and flexible: You can carry out many operations on RDDs to accomplish different tasks.

3. What is a DataFrame?(This is an important PySpark interview question)

A DataFrame is a distributed collection of data structure segregated into rows and columns. These columns are named. It is far more optimized than R or Python. PySpark data can run on various machines within the span of a single second. It passes the efficiency criteria, as it makes handling collected data much easier.

4. What are the Key Characteristics of PySpark?

- Nodes are abstracted – You cannot directly access individual worker nodes.
- APIs for Spark features – PySpark provides APIs to use Spark’s core features.
- Based on MapReduce, PySpark follows the MapReduce model, letting you define map and reduce functions.
- Abstracted network – Network communication happens implicitly, without manual handling.

5. A PySpark Interview Question could be: Is PySpark faster than pandas?

Absolutely, PySpark is faster than Pandas. With PySpark, we have the option to run tasks in parallel on many machines. That too in one go. This feature is not available in Pandas.

6. What are Spark files?

SparkFiles is a tool used to load files into your Spark application.

You can use:

sc.addFile() to add files

SparkFiles.get() to retrieve or resolve the file path.

The two class methods in the SparkFiles directory are getRootDirectory() and get(filename).

7. What are PySpark serializers?

Serialization is primarily built for performance tuning. It tunes or changes the data into a format that can be stored on a disk or sent over a network.

The two types of serializers are

The PickleSerializer takes the help of Python’s Pickle to serialize objects. It supports all Python objects.

The MarshalSerializer is quicker, but it supports only limited object types.

8. What is a Parquet file in PySpark? 

This question is very important under PySpark Interview Questions 

A Parquet file is a columnar storage format where columns, instead of rows, organize data. Spark can efficiently read and write data thanks to this structure. It is particularly well-suited for large datasets, as it is faster and more space-efficient. It also reduces overall storage requirements.

9. What is PySpark SparkContext?

SparkContext gives the entry point to any Spark feature. It allows your Spark Application to access the cluster.

10. What are the techniques for filtering data in PySpark DataFrames?

You can use the filter() or where() methods:

df_filtered = df.filter(df["column"] > value)

11. Can you join two DataFrames in PySpark? How?

Yes, You can use the join() method in PySpark:

df_joined = df1.join(df2, df1["key"] == df2["key"], "inner")

PySpark supports different join types such as inner, left, right, full, semi, and anti joins.

12. What is PySpark StorageLevel?

PySpark StorageLevel defines how an RDD is stored. It decides where data is kept- in memory, on disk, or in both. It also regulates whether RDD partitions are replicated and if the data should be serialized.

PySpark Interview Questions for Experienced

Let's level up our game with  PySpark Interview Questions for professionals. Under this topic, you will come across various advanced questions.

1. How can you calculate Executor Memory in Spark?

To calculate executor memory, you need to know:

Total cores per node

Number of executors per node

Available memory per node

Formula

Reserved Memory is usually 5–10% of the total node memory (kept aside for system processes and Hadoop daemons).

Example Calculation

Total node memory = 64 GB

Reserved memory = 8 GB (for OS + daemons)

Executors per node = 4

So, each executor gets 14 GB of memory.

This ensures Spark jobs use memory efficiently without hitting OutOfMemory (OOM) errors.

2. Convert a Spark RDD into a DataFrame

There are two common ways to convert an RDD into a DataFrame in Spark:

Using the toDF() helper function

import com.mapr.db.spark.sql._

val df = sc.loadFromMapRDB()

  .where(field("first_name") === "Peter")

  .select("_id", "first_name")

  .toDF()

Using SparkSession. createDataFrame

def createDataFrame(RDD, schema: StructType)

3. How do you use Window functions in PySpark to calculate row-wise metrics?

You can use the Window class to perform operations like ranking, running totals, or moving averages.

from pyspark.sql import SparkSession

from pyspark.sql.window import Window

from pyspark.sql import functions as F

spark = SparkSession.builder.appName("WindowFunctions").getOrCreate()

data = [("Alice", "HR", 3000),

        ("Bob", "HR", 4000),

        ("Charlie", "IT", 3500),

        ("David", "IT", 4500),

        ("Eve", "Sales", 5000)]

columns = ["Name", "Department", "Salary"]

df = spark.createDataFrame(data, columns)

# Define window partitioned by department and ordered by salary

windowSpec = Window.partitionBy("Department").orderBy(F.desc("Salary"))

# Rank employees by salary within each department

ranked_df = df.withColumn("Rank", F.rank().over(windowSpec))

ranked_df.show()

This is an advanced PySpark interview question, since window functions are widely used in analytics pipelines.

4. How do you perform a Broadcast Join in PySpark?

Broadcast joins are used to optimize joins when one dataset is small enough to fit in memory.

from pyspark.sql import SparkSession

from pyspark.sql import functions as F

spark = SparkSession.builder.appName("BroadcastJoin").getOrCreate()

# Large dataset

data_large = [(1, "Alice"), (2, "Bob"), (3, "Charlie"), (4, "David")]

df_large = spark.createDataFrame(data_large, ["ID", "Name"])

# Small dataset

data_small = [(1, "HR"), (2, "IT"), (3, "Sales"), (4, "Finance")]

df_small = spark.createDataFrame(data_small, ["ID", "Department"])

# Perform broadcast join

df_joined = df_large.join(F.broadcast(df_small), "ID")

df_joined.show()

We have come to the end of PySpark interview questions and answers for experienced candidates.Great job keeping up!

5. PySpark Coding Interview Questions and Answers

How Can I Determine Spark's Total Unique Word Count?

Steps:

Load the text file as an RDD

lines = sc.textFile("hdfs://Hadoop/user/test_file.txt")

Split each line into words

words = lines.flatMap(lambda line: line.split())

Convert every word to a key-value pair (word, 1)

wordTuple = words. map(lambda word: (word, 1))

Count word occurrences using reduceByKey()

counts = wordTuple.reduceByKey(lambda x, y: x + y)

Collect and print the results

print(counts.collect())

6. How Can I Use Spark to Determine Whether a Keyword Is Present in a Large Text File?

lines = sc.textFile("hdfs://Hadoop/user/test_file.txt")

foundBits = lines.map(lambda line: 1 if "my_keyword" in line else 0)

total = foundBits.reduce(lambda x, y: x + y)

if total > 0:

    print("Found")

else:

    print("Not Found")

7. How Can I Link Hive and Spark SQL?

Steps:

Place the Hive configuration file

Copy hive-site.xml into Spark’s conf/ directory so Spark can read Hive settings.

Use SparkSession to query Hive tables

from pyspark.sql import SparkSession

# Enable Hive support

spark = SparkSession.builder \

    .appName("HiveConnection") \

    .enableHiveSupport() \

    .getOrCreate()

# Run Hive query

result = spark.sql("SELECT * FROM ")

result.show()

8. How do you remove duplicate rows in a PySpark DataFrame?

You can use the dropDuplicates() or dropDuplicates(subset=[...]) method.

from pyspark.sql import SparkSession

spark = SparkSession.builder.appName("RemoveDuplicates").getOrCreate()

data = [("Alice", 25), ("Bob", 30), ("Alice", 25), ("David", 40)]

columns = ["Name", "Age"]

df = spark.createDataFrame(data, columns)

# Remove all duplicates

df_no_duplicates = df.dropDuplicates()

df_no_duplicates.show()

# Remove duplicates based only on 'Name'

df_no_duplicates_name = df.dropDuplicates(["Name"])

df_no_duplicates_name.show()

This is a very common PySpark interview question since deduplication is widely used in ETL pipelines.

9. How do you calculate aggregate functions like average, sum, and count in PySpark?

You can use the groupBy() with aggregation functions (avg, sum, count).

from pyspark.sql import SparkSession

from pyspark.sql import functions as F

spark = SparkSession.builder.appName("Aggregations").getOrCreate()

data = [("Alice", "Sales", 2000),

        ("Bob", "Sales", 3000),

        ("Charlie", "HR", 4000),

        ("David", "HR", 2500),

        ("Eve", "IT", 2200)]

columns = ["Name", "Department", "Salary"]

df = spark.createDataFrame(data, columns)

# Group by Department and calculate aggregates

agg_df = df.groupBy("Department").agg(

    F.avg("Salary").alias("Average_Salary"),

    F.sum("Salary").alias("Total_Salary"),

    F.count("Name").alias("Employee_Count")

)

agg_df.show()

This type of coding question is asked to test knowledge of groupBy + aggregations in PySpark DataFrames.

10. How Can I Work with Structured Data in Spark SQL Using Domain-Specific Language (DSL)?

Example:

val df = spark.read.json("examples/src/main/resources/people.json")

df.show()

df.select("name").show()

df.select($"name", $"age" + 1).show()

df.filter($"age" > 21).show()

df.groupBy("age").count().show()

Using DSL in Spark SQL, you can select, filter, transform, and aggregate structured data in a clean and intuitive way.

Spark Program to Check if a Given Keyword Exists in a Huge Text File

from pyspark import SparkContext

sc = SparkContext("local", "Keyword Search")

textFile = sc.textFile("path/to/your/text/file.txt")

keyword = "yourKeyword"

exists = textFile.filter(lambda line: keyword in line).count() > 0

if exists:

    print(f"The keyword '{keyword}' exists in the file.")

else:

    print(f"The keyword '{keyword}' does not exist in the file.")

11. How to Work with Different Data Formats in PySpark

from pyspark.sql import SparkSession

spark = SparkSession.builder.appName("DataFormats").getOrCreate()

df_json = spark.read.json("path/to/file.json")

df_parquet = spark.read.parquet("path/to/file.parquet")

df_avro = spark.read.format("avro").load("path/to/file.avro")

df_json.write.json("path/to/output/json")

df_json.write.parquet("path/to/output/parquet")

df_json.write.format("avro").save("path/to/output/avro")

12. Lazy evaluation in PySpark

Spark memorises the instructions when ever it is being operated on any dataset. An RDD does not execute a transformation, like a map(), immediately when it is called. Lazy evaluation is a feature of Spark that helps optimize the entire data processing workflow, and transformations are not executed until you take an action.

Conclusion

We have covered the topics of DataFrames, RDDs, and Lazy Evaluation in this blog. We have also included PySpark coding interview questions and answers so that you will be code-ready. We hope this PySpark interview questions guide will be helpful in your preparation.

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Good luck with your next interview!

Faqs

Can I expect coding-based PySpark interview questions?

Yes. Many interviews include coding tasks like filtering, joining DataFrames, or writing word count programs.

Are PySpark interview questions mostly theoretical or practical?

Normally, PySpark interview questions include both. Basic theory, hands-on coding, and real-world problem solving are asked.

What are some advanced PySpark interview questions?

Advanced questions often involve optimization, Spark architecture, shuffle operations, and broadcast joins.

What are scenario-based PySpark interview questions?

Scenario-based PySpark interview questions are mostly real-world problems. Examples include handling skewed data or optimizing a slow job.